WW1 French Prototypes

Renault Char d’Assaut 18hp – ‘Renault FT’ Development

ww1 French TanksFrance (1915 – 17)
Light Tank – Around 3,500 Ordered

When the Republic of France entered World War 1 on 3rd August 1914 against the German Empire, few could have had any concept of the scale and duration of the war which was to follow. Having already fought the nascent German Empire in 1870-1871 and lost the territory of Alsace-Lorraine in a humiliating defeat, France was determined not to repeat its failures, yet entered WW1 unprepared for a new type of warfare dominated by artillery and rapid-fire machine guns. Just as other nations soon found, the men of their respective armies, regardless of personal heroism, were no match for a well-prepared defense or machine gun fire. Machines were to be a key to victory, new armored machines carrying guns to meet the enemy and, to this end, France developed a tank which was to shape their future designs for many years and become an icon of WW1 – the Renault FT.


The Republic of France was to suffer appalling casualties in WW1. The Western Front, large swaths of which cut through Eastern and Northern France, was the scene of some of the bloodiest fighting ever seen in Europe and was brutal grinding butchery for four years from 1914 until 1918.

Despite numerous assaults by the British, French, and Germans on the Western Front, neither side could gain an advantage, and the war descended into a static war of attrition, with troops having to shelter below ground from the murderous effects of artillery and machine gun fire. The industrialization of Europe had created the situation where artillery and machine guns could bring warfare to a standstill and the military tactics of the belligerents had not adequately kept pace with technology.

Just as modern technology and industrialization had created the circumstances for the static war, they also held out the prospect of a solution for it as well. Automobiles and aircraft were in their infancy, but were rapidly turned to war uses and armored cars had actually been in development in many nations prior to the war. It is no surprise then that, with the slaughter taking place in Europe between the Great Powers, as armored cars could not traverse the shattered ground, tracked vehicles were considered by Britain, France, and Italy (suffering its own stagnant warfare on its northern front against Austria-Hungary) all around the same time.

Tracks to get over the broken ground would then need armor to protect the crew, and weapons to bring the fight to the enemy. The concept of what was to become the tank was an inevitability, but these allied powers had little in the way of coordination in the early days of the war, and each ran their own programs with varying degrees of success.

A French Solution

Unlike the British, who by 1915 had abandoned the Holt track system, and by the end of the year abandoned other ‘low-slung’ types of track in favor of an ‘all-round’ system, the French were still looking at the Holt system for their own designs. There was some parallel development in France, with some work on machines such as the Schneider CA1 and St.Chamond, but one man stood out with a different view, that of a smaller machine better suited to the conditions on the front lines.

The man behind all of this was the French ‘Father of the Tanks’ (French: ‘Père des chars’), Jean Baptiste Eugene Estienne (1860 – 1936). With an aptitude for mathematics and science, he had joined the French Army in 1883, becoming an artillery officer. By the start of WW1, Estienne was a Colonel commanding the 22nd Artillery Regiment in combat.

With a first-hand experience of the power of modern weapons, such as his own artillery, but also witnessing the devastation from machine guns, he rapidly saw the need for some kind of protective shield. By the middle of 1915 (at a time when the British were already working on what was to become Little Willie), Col. Estienne learned of a tracked barbed-wire cutter based on the Holt chassis and developed by Eugene Brille of the Schneider Company.

It was not much of a logical extension for Col. Estienne to consider this as a suitable vehicle on which to mount some armor. His efforts failed though until December 1915, when he finally convinced Marshal Joseph Jacques Cesaire Joffre (1852 – 1931) of the validity of his idea.

Unknown to Col. Estienne at the time was that Schneider had already been developing its own vehicle with exactly the ideas he had in mind; armor and a gun on the Holt chassis. That tank became the Schneider CA-1 and Col. Estienne witnessed trials of that vehicle on 9th December 1915. The Schneider design had some very serious shortcomings, not least of which was the mounting of the main gun in a peculiar fashion on the side of the machine, seriously limiting its combat potential.

The engineering-orientated mind of Col. Estienne must have been triggered into action by this experience, as on 21st December 1915 (the day the Schneider CA-1 was authorized for production), he reached out to the famous industrialist Louis Renault (1877 – 1944) with his own ideas for a better vehicle – one designed from scratch to do the job rather than just a modified tractor. Monsieur Renault was, at first, reluctant to embark on building a tank, but by the middle of July 1916, he confirmed to Col. Estienne that he was indeed working on a light tank.

The war conditions for France had not improved since 1914, but waiting until the middle of 1916 had now put France well behind Great Britain in terms of tank development. Lagging behind, but now aware of British developments, the French actually tried to convince the British to hold off on using their own tanks for the first time until they were ready with theirs. No doubt, it was a fine idea to have a coordinated approach, but the slaughter underway each day was not abating and the British were anxious to try and break the stalemate which was also costing them so dearly.

Following the British use of tanks in September 1916, the French were now under no illusions about the true potential of these new weapons and, on 30th September 1916, Colonel Estienne, as the most senior French officer with the knowledge, interest, and experience in such matters, was appointed as Commander of the newly formed French armored corps, known as the ‘Artillerie Speciale’ (English: Special Artillery).

Conception and Development

The idea for a tracked tank had first been brought to Louis Renault’s attention by Colonel Estienne back in December 1915, but he had at first been reluctant to postpone or divert production away from other military work for a new and unproven weapon. By the summer of 1916, however, this view had changed, probably as a result of his factory being subcontracted to produce parts for other firm’s tank designs, although he had been doing some preliminary work on a tank design nonetheless. M. Renault confirmed to Col. Estienne in July that year that he was working on a light tank design, although how much of Col. Etienne’s ideas had to that point been absorbed or used by M. Renault is debatable. What is known though, is that Col. Estienne had been unimpressed by the ‘big box’ tanks and foresaw instead a mass of smaller, light tanks acting like a swarm of bees, overwhelming the enemy with a rapid advance, and multiple weapons delivering fire from all quarters during an advance. The conversation on 21st December 1915 between Col. Estienne and M. Renault showed that what was wanted was a tank of not more than 4 tonnes in weight, a two man crew, a top speed of up to 12 km/h, and a machine gun in a turret on top. M. Renault agreed to produce a wooden mock-up of such a design by October 1916.

This new tank would have to be mechanically simple to ease demands of production, which was already at full stretch for the war effort, be constructed by relatively unskilled labor, as most of the skilled workforce was now in uniform fighting, and be cost-effective. The Army could not afford enormous and expensive vehicles that had so far proven to be somewhat unremarkable, like the Schneider CA-1 and the enormous St. Chamond. Smaller, cheaper vehicles, and lots of them were the order of the day.

The ungainly St. Chamond was well armed but suffered from woeful mobility off-road due to the outdated track system and the size of the projection at the front. Source: Pinterest

M. Renault was director of the Société des Automobiles Renault (Renault Automobile Company), but other key individuals at the firm and connected to it were involved in aspects of the design, such as M. Rodolphe Ernst Metzmaier (industrial designer), and M. Charles Edmond Serre. They were to fulfill Estienne’s vision of small fast tanks within their own manufacturing capabilities and what they developed was to become one of the most famous tank designs of all time, the Renault FT.

“L’audace, l’audace, toujours l’audace!” – A Bold Design

In order to be mass produced, this new tank would have to seize upon the enemy quickly and boldly destroy it with machine gun fire. To do this, it was shorter, narrower, and lower than the CA-1 or its huge cousin, the St. Chamond. Smaller would mean less space for the crew and this was reduced to the bare minimum – just 2 men. One man would drive and the other would command the tank and operate the weapons.

Using a single weapon with all-round fire in a turret was not a new idea by any means, and was already in widespread use on armored cars, and even on Little Willie and some earlier British designs, although the British later switched to side-mounted guns instead. The key advantage of a turret, as used for this little French tank, was that it concentrated firepower in one place, for one man, which allowed the tank to remain small and yet carry useful firepower for the assault. A turret was quite simply the only practical solution to the problem of providing fire to all sides on a light tank. This was realized by the British for their own ‘light’ tank, the Medium Mark A Whippet, which started development in December 1916 and which, in its early form, was the ‘Chaser’ and had a single turret for firepower. Whereas that turret was abandoned in favor of multiple machine guns all round in a large casemate, the Renault was too small for that to be an option, so it was a turret or nothing.

A British Medium Mark A ‘Whippet’ passing a group of German prisoners of War on the Western Front. Source: US National Archives

With the driver placed in the front, the commander/gunner sat behind him to operate the turret and weapon, and the engine at the back, the Renault FT is seen by many as being the first ‘modern tank’ although such comparisons are superficial at best. The most important part of this Renault tank is often ignored by historians and was, in fact, the separation of the engine from the crew. The British tanks, for example, did not do this vital safety-step until the Medium Mark B in 1918, and neither the French Schneider CA-1 nor the St.Chamond did this either. The bulkhead protected the crew from the stifling heat and fumes of the engine and, perhaps more importantly, from potential engine fires.

The Schneider CA-1 had a most unusual arrangement of the primary armament off to one side but was more hampered by a general lack of mobility. Source: Public Domain

M. Renault finished his wooden mock-up on schedule in October 1916 and showed it to Col. Estienne. This design set the basic layout for the vehicle over its life, although each part was subject to changes at one point or another. For this wooden mock-up, the turret was nothing more than a simple cylinder with the only armament. Stood inside the tank, with his head and shoulders inside the turret, was the commander/gunner who could use a hatch in the turret to climb in and out. The driver, however, sat at the front, would have to use a hatch on the front deck of the tank, a very dangerous prospect for him if he had to get out facing enemy fire.

Original wooden mock-up for the Renault FT with the cylindrical turret and side removed, showing the internal arrangements. Source:, colorised by Jaycee Davis

Perhaps the biggest hurdle to the development of the FT was not the relative merits or deficiencies of the design, but the French military mindset. For a big battle, it was logical that a big assault, a big gun, or a big weapon was the solution and the concept of small, light tanks was perhaps incongruous in the face of the large British tanks and the no less huge St. Chamond.

The prototype was tested and, despite some reservations, was accepted for service in May 1917, when Marshal Henri Philippe Pétain (1856 – 1951) replaced General Robert Georges Nivelle (1856 – 1924) as Commander-in-Chief of the French Army following the disastrous Nivelle Offensive and French Army mutinies. Marshal Pétain was an advocate for the use of tanks, supportive of Estienne, but also with an eye not just to its potential as a weapon but also as a morale booster for the war-weary infantry who were bearing the brunt of the fighting. Later, he was to order that all of the trucks carrying these tanks to the frontline have written in large characters on their backplate “Le meilleur ami de l’infanterie” (English: ‘infantry’s best friend’).

Brigadier-General Leon Augustin Mourret (1849-1933) though, Director General of the Motor Services, was reluctant to adopt the Renault design which, at the time, was being developed under the working title of char mitrailleur (English: machine gun vehicle). He was likely conscious of interfering with the production of other equipment such as trucks, tractors, and artillery.

A new mock-up char mitrailleur was presented on 30th December 1916 to the Consultative Committee of the Assault Artillery. Gen. Mourret remained unimpressed, however, despite no longer being the Minister in charge, complaining the vehicle was too light, with the center of gravity too far back, making it unstable, and that there was inadequate ventilation for the crew. Other suggestions included a wider hull and turret, and storage for up to 10,000 rounds of machine gun ammunition (‘normal’ carriage was just 1,820 rounds).

The basic design from October 1916 had been set but there were still deficiencies. The cylindrical turret for the commander/gunner, who had to do both jobs simultaneously, was only fitted with crude vision slits making for very limited observation of the ground around the tank. The body of the tank was a large riveted box with a bulbous back end housing the engine. At the back of this body was a small starting handle for the engine and there was a small air intake on top.

The suspension changed little from the prototype to production, although the vertical spring in the center of the suspension which connected to the arm holding the return rollers was removed for production as it had little value.

Wooden mock-up showing the very large body at the back of the tank and the cylindrical turret. Source: Public Domain, colorised by Jaycee Davis

The arrangements of the body and turret were not ideal and wasted space and weight, both of which were critical. By December 1916, significant modifications to both had been made. The hull’s back was cut much shorter, saving a lot of weight, and the small cylindrical turret was replaced with a much wider hexagonal one with a cross-shaped vision slit in each face. The turret also overhung the side of the hull, necessitating small flanges to be attached to the hull to cover the bottom of the turret where it projected. All of the plates used in this revised design were flat and to be made by riveting to a steel frame inside the vehicle.

Rodolphe Metzmaier with the revised, December 1916 FT. Note that the armament is a single machine gun, the shadow of it on the wall behind it is misleading. Source:, colorised by Jaycee Davis

Some of the suggestions from the December 1916 examination were acceptable to the design team, but others were clearly impractical. The Consultative Committee of the Assault Artillery then voted on production; the vote was seven-to-three in favor of production and orders for 100 char mitrailleurs followed. That order was increased in February 1917 to 150 vehicles, although Col. Estienne had been pressing for orders for 1,000.

The FT-17 That is Not

It is important to note that the name ‘FT’ was never an abbreviation or acronym, despite numerous books and websites claiming explanations for the initials including ‘Faible Tonnage’ (English: ‘low tonnage’ – ‘light weight’) or ‘Franchisseur de Tranchées’ (English: ‘trench crosser’). The name ‘FT’ was none of those, it was just a factory code for this char mitrailleur, nothing more, nothing less. All the Renault tank products were issued with a two letter code serving to identify and differentiate them. FT simply followed FS, and would, in turn be followed by an FU (which was later used for a heavy Renault lorry), then FV.

The Renault FT is also often referred to as the ‘FT17’ or ‘FT-17’, although this specific naming was never acknowledged by Renault or any official working on the project. The ‘17’, of course, was in connection to the year 1917, as it was customary for many French weapons of the time creating the ‘char leger Renault FT modèle 1917’ (English: Renault Fast Tank Model 1917). The ‘FT-17’ designation though, was only later referred to, after the war. For the duration of WW1, it was simply the Renault FT for convenience.


A single prototype vehicle for this new version of the FT was delivered in January 1917 and performed first trials at Renault’s factory at Boulogne-Billancourt, before being sent by Col. Estienne to the Artillerie spéciale (English: Special Artillery) proving grounds at Champlieu, North-East of Paris, for final corrections before its official make or break trials in April that year.

If getting an order for a prototype and small production for his light tank idea was a win, then in April 1917, even before the trials, Col. Estienne was triumphant. The Consultative Committee of the Assault Artillery was on his side and voted in favor of his plans for production of 1,000 examples. This triumph was further crowned by General Nivelle, who was not an opponent of tank production, was now a convert to armored warfare and supported this production.

Official trials took place at Marly, South-East of Lille, between 21st and 22nd April 1917. Here, during comparative trials against the Schneider CA-1 and St.Chamond tanks, the diminutive FT was shown to be superior. Perhaps buoyed by his success in winning over General Nivelle and the proof of concept beating any other tank the French had, Col. Estienne then suggested that this machine gun armed tank be fitted with a small 37 mm gun creating a ‘char canon’. It had never been intended to carry anything other than a machine gun until this point, but he felt that a version of the 37 mm modèle 16TR infantry cannon could be made to fit and would provide some useful support to infantry in attacking enemy defences. A machine gun, after all, was almost useless against an enemy bunker, but a small gun could fire explosive shells right where they were needed instead of relying on field artillery behind the assault. There was insufficient space for both a cannon and a machine gun. But, as these vehicles were to be used in groups, they would be able to provide complementary fire for each other, with the char canon taking out the strongpoints and the ‘char mitrailleur’ taking out the infantry.


General Nivelle might have been converted to the value of the tank, but M. Albert Thomas was not to be convinced. The small space inside the turret effectively limited it to a commander not more than 1.68 m tall (5’6”). This, combined with concerns over the instability of the vehicle, the ventilation for the crew, inadequate ammunition capacity, and the difficulty of one man commanding and operating the gun, led to him suggesting an additional crew member be added to operate the main armament. The addition of a third crew-member would mean a total redesign of the vehicle to accommodate him, but would in fairness have solved a problem that was to plague French tanks for a generation, the tiny one-man turret.

Regardless of his concerns, right or wrong, it was too late. General Nivelle’s offensive on the Chemin-des-Dames was an utter failure, with great loss of life, and further delays to a tank program were no longer acceptable. M. Thomas though, left on an overseas trip, and in his absence, Col. Estienne simply worked around him. He demonstrated the tank for officers from the disastrous Chemin-des-Dames offensive, including those who had fought with the Schneider and St.Chamond tanks in what was France’s first use of tanks – they were convinced. Their insistence and the political pressure of a failure to break the stalemate on the Western Front now persuaded even the reluctant General Mourret that they were needed urgently, and he overruled M. Thomas’ order. The original order for 1,000 vehicles was replaced with a new order for 1,150 vehicles, consisting of 500 of the original char mitrailleur armed with the 8 mm Hotchkiss machine gun and 650 of the new char canon fitted with the 37 mm gun.

Pétain, the advocate

Marshal Pétain, himself an artillery officer, knew Colonel Estienne and had, in general terms, agreed on the need for tanks and that small, fast tanks could overwhelm an enemy unlike the large and slow Schneider CA-1 and St. Chamond. In a brutal war of attrition, production played a part too, and the tiny FT had a small manufacturing footprint. Five FTs could be built for every heavy tank and those heavy tanks were not armored sufficiently to stop German artillery fire. Instead of armor then, these small tanks would rely on their small size and good mobility to avoid enemy fire. Pétain did not need much additional convincing post-Chemin-des-Dames and increased the order from 1,150 to 3,500 vehicles instead. The design undoubtedly had significant flaws but it had a single massive advantage over every other design available – it worked. Rather than wait on new and improved design Pétain made use of what he had, a working design, and one intended for a new offensive in Spring 1918.

To smooth out production, the hurdle that was M. Albert Thomas was removed too, replaced in September 1917 by the Under Secretary of State for Artillery and Munitions, industrialist M. Louis Loucheur (1872 – 1933). Nothing was going to get in the way of Pétain’s new tank. So when, shortly after placing this order, it was found that Renault would not be able to produce all these vehicles itself in time, Renault waved any patent rights issues, allowing production to go to other factories. Contracts were eventually issued to Berliet, Somua, and Delaunay-Belleville as well as consideration of production outside France in Italy and the United States in order to produce the numbers demanded.


The development phase of the Renault FT, one of the most identifiable and famous tanks of all time, had concluded. The vehicle would undergo significant modifications and trials with various nations and see action beyond WW1 in many theatres. It was not a perfect tank by any means, the tiny one man turret, the front access for the driver, the lack of a radio, and the relatively weak armament would plague the vehicle and its many variants, but the design was to prove the most successful French tank of WW1 even if it nearly never happened at all.

Illustration of the 1916 design of the FT produced by Yuvnashva Sharma, funded by our Patreon campaign.


Renault. (1917). Renault Char d’Assault 18hp.
Canon de 37 SA pour Chars Légers 1918
Lt. Goutay. (1920). Manuel pratique du Char Renault
War Office. (1922). Instruction sur l’arrimage du lot OI RI des Chars Légers Renault
War Office. (1931). Instruction sur l’Armement et le Feu dans les Chars Légers
War Office. (1935). Instruction sur l’Armement et le tir dans les unités de Chars Légers
Bruché, Col. (1937). Manuel d’Instruction pour les Unités de Chars Légers – Canon de 37 SA –
Gale, T. (2013). The French Army’s Tank Force and Armoured Warfare in the Great War. Ashgate Press, England
Vauvallier, F. (2014). The Encyclopedia of French Tanks and Armoured Fighting Vehicles 1914-1940. Histoire and Collections Publishing, France
Zaloga, S. (2010). French Tanks of WW1. Osprey Publishing

Click the image to buy the book!

WW1 French Prototypes

The Boirault Machine

ww1 French Tanks France (1914-20)
Prototype – 2 Built

Probably the most unlikely looking of all tank designs is the famous Boirault machine or, to give it its full name, the Fortin Automobile ‘la Machine Boirault écrase barbelé’ (Eng: The Barbed Wire Crushing Boirault Machine). Usually used as an example of bad design or for mockery, these machines were an ingenious and inventive means of crossing trenches and broken ground and were not the product of some random inventor. These designs came from the highly respected and very well experienced French Engineer Louis Boirault. Boirault was an undenied expert in railways in his position in the state rail system. Specifically, he was an expert in railway couplings, and between 1900 and the 1920s, having had amassed over 120 patents to his name, mostly for railway connected matters.

Monsieur Louis Boirault (right) during his work with the French National Rail System before the war. French National Library Reference #6928904

When, in August 1914, Germany declared war on France, few could have envisaged the mostly static grinding butchery that the war would become. Most armies were grossly unprepared for the mass slaughter brought about by the industrialization of Western Europe, with machine guns and artillery becoming the predominant weapons of war rather than the rifle or lance. It was not long, however, before the armies settled into lines of defense with each side unable to inflict a decisive breakthrough and defeat the other. By the end of 1914, with casualties mounting rapidly (over 300,000 men by the end of the year,) inventive minds across Europe were awaiting a breakthrough, so it is no surprise that a man such as Boirault should turn his engineering prowess to the difficult question of how to take the war to the enemy across open ground cut with trenches, guarded by belts of barbed wire, and covered by machine gunfire. An armored machine was the inevitable outcome, but wheeled vehicles could not cross such ground and, in 1914, there were few tracked machines available in France on which to base such a vehicle. Whilst the French designs eventually ended up using the Holt tractor chassis (a chassis rejected early in 1915 by the British) there was, with the war ground to a halt, in 1915 a period of experimentation looking at methods of attack by machine. Monsieur Boirault’s idea would stand out amongst many others as the most original.

Origins December 1914 to February 1915

In December 1914, Louis Boirault and his company (the Boirault Company) started considering the question of crossing no man’s land (the area between the front lines of the opposing armies) and proposed a solution to the French War Ministry. With few other options, the War Ministry authorized production on 3rd January 1915, and under the eye of a commission to supervise the invention led by Paul Painleve (Minister for Inventions), construction began. By February 1915, his considerable experience with railways led to his design ideas being presented to the French military, which were evaluated along with various other, often odd ideas, offering solutions to the same problem.

Theory of design for the machine as shown in French Patent FR513156(A) 1919.

An Inventive Design

Instead of wheels, he envisaged tracks. Not the sort of tracks used in some agricultural vehicles of the age, but much more akin to what he knew: train tracks. Obviously, you cannot lay train tracks for a train to attack the enemy, so the answer is to simply bring them with you. With two parallel rails attached horizontally by 4 steel girders, this machine used 6 sets of these frames to carry the machine. The ‘rail’ parts and the ‘sleeper’ parts spanning between them across the frames would carry the load of the vehicle on the soft ground and as the machine advanced they would simply be picked up behind and carried back over the top of the vehicle to be laid in front once more. This is exactly the same principle as other track layers but the single-track nature and sheer size of the tracks in question make it look more unusual than it actually is as an idea.

Theory of frame-related movement. French Patent FR513156(A) 1919
Boirault Machine during testing. Source: Vauvallier via the Touzin Collection

Each frame was simple and rugged and obviated the problems found with other tracked vehicles of the time. There was no track sag (where the tracks drop away from the body of the vehicle or running gear), there was no lateral slippage (tracks slipping off the wheels sideways), and, most importantly, the six frames required just 12 pins to attach them together, which reduced the chances of a pin failing because they could be made very substantial, like a railway car coupling. These three problems that plagued early tracked vehicles were ‘solved’ so to speak, in one simple move, but the price of this solution was also, eventually, to be its greatest failing.

The giant frames on which the machine ran. Also, note the complex arrangement of drive chains. Source:
The first Boirault machine showing the angularised nature of the frames nicely. Source: Granier

The machine inside this 6-frame-track run was an unusual rectangular based pyramid with the edges of the pyramid constructed from the same type of heavy steel girders used in the frame sections. Where these pieces met the frame at the bottom (2 contact points per side) and at the top of the triangular sides (one per side) there was a heavy steel roller along with a large square section ‘doughnut’ forming a path through which the frame sections would run. This was a very rigid and robust system for which there would be no movement at all of the track. Effectively, it was as if a train’s wheel was being held firmly onto a track and taking all of the weight. Within this pyramidical structure, at the heart of the machine, lay the Aster petrol engine. This engine drove the tracks by means of steel drive chains but was underpowered for the task and capable of propelling the machine at just 1.6 km/h (1 mph). It is worth noting that at least one contemporary source states that the 80 hp petrol engine used came from the Filtz agricultural tractor.

Under this engine, and within the body of the machine, a crew would have to be accommodated somewhere, along with fuel, and, at some point, some kind of offensive weaponry. The drive was at the top of the machine. Whilst this had the huge advantage that the drive could not get clogged with wire or mud, it also meant that the crew sat underneath all of this, making it harder to see, and raised the center of gravity for the machine. The bottom of the pyramidical vehicle can be seen in photographs to have a curved bow and stern section and would slide along the frame on its wheels crushing down any obstacles such as barbed wire staves in its way.

Two views of the Boirault prototype no.1 during testing in 1915. Source: Scientific American


The design, despite being functional and able to move under its own power, was unsuitable for war. The French military authorities found the machine to be robust and ingenious but the faults were obvious. Firstly, it was huge, and perhaps it was because the size and slowness of it some officers christened this ‘Appareil Boirault’ machine with the tongue-in-cheek moniker of ‘Diplodocus militaris’ – a military dinosaur (the Diplodocus was a large long-necked herbivore living in the late Jurassic period about 150 million years ago). Measuring 8 meters long, it was still narrow enough as a machine (just 3 meters wide) to be transported by rail, but this would have to be done partially disassembled because, at 4 meters high, it would not clear any bridges. The height was also a considerable problem, it would be impossible to hide from enemy observation and very vulnerable to enemy fire. With the engine at the top, it would become crippled quickly, although the lack of conventional track plates would at least render these huge frames safe from damage by concentrated machine-gun fire on them. At just 1.6 km/h (1 mph), the machine would be unable to evade fire, and being easily targeted would have to carry a large weight of armor which would make it even less mobile. Clearly, this was all impractical even though these frames enabled it to cross trenches up to 3-4 meters wide. The greatest fault though was steering. With just a single track and no means of altering power to one side or another or hydraulic adjustment on the machine, the machine would only be able to move in a straight line. Whatever direction it was pointed in when it set off would be its direction, forwards or backward, making it even easier to hit as a target and also rendering it likely to be thrown off course by undulations in the ground.

If that happened, the two-man crew (presumably a driver, and a commander who would have to operate whatever weapon might have been mounted eventually), would have to exit the vehicle and laboriously use jacks to lift one side of the vehicle from the ground to bring it back on course: a suicidal endeavor in the middle of no man’s land.

According to the historian Alain Gougard, these faults were published in an official report on the subject on 17th May, and consequently, on 10th June 1915, this first machine was abandoned. The historian Francois Vauvallier, however, gives the dates of the test not in February 1915, but on 10th April 1915, although it is possible that testing actually spanned that period. He also provides the date of abandonment of the design as 21st June 1915, not the 10th, but either way, by the end of June 1915, it was officially abandoned.

Boirault machine crushing its way through a barbed wire entanglement during 1915 trials. Image: Steven J. Zaloga

A New Hope – A Second Trial

All was not lost for Monsieur Boirault though. This was still the middle of 1915 and the French Army still did not have an effective tank. In context, the British had yet to perfect the all-steel tank track, so it can be understood that this was still very early on in the development of tank warfare. Boirault was stubborn in his insistence as to the viability of his design and he had been correct that the design worked. The resulting efforts by him pressing his case meant that the French Government created a new commission to oversee his work and authorized him to produce an improved version of this machine. Howard states that this improved machine was scheduled for trails to take place in November 1915, but this second phase is not mentioned at all by Vauvallier.

The enormity of the machine is apparent in this image. The chain drives from the engine going upwards to the drive gears can also be seen as can be ballasted weights on the lower part of the vehicle. Source:

This second trial, organized on 4th November 1915 and taking place on the 13th, showed once more that the machine moved. This time it was laden with 9 tonnes of ballast to simulate arms and armor which would be fitted and albeit still very slowly, merrily plowed through a barbed-wire entanglement 8 meters deep and over a two-meter wide trench.

The primary modification to the machine appears to have been in the steering. Previously, a single large external jack was used, but this November trial demonstrated an internal system of smaller jacks operated from inside the machine. It is not clear when these were fitted, but given the criticisms of the machine from the spring trials and the lack of obvious visual changes, the addition of these smaller internal jacks is a logical assumption. Either way, turning was very slow, had to be done from a halt and was limited to a maximum of 45 degrees.

The modifications proved insufficient to overcome the inherent problems of the design and once more the machine was rejected.


With the first machine having proved his theory at least technical sound, if not very practical, Boirault used his company and experience to produce a second vehicle. This new machine was substantially different from the first machine incorporating the same ‘over the top’ single track principle but substantially smaller and with a much more compact track run. Vauvallier states that this machine was already underway in either design or construction by the time of the November 1915 trials of the first machine.

A New Design


The essential principle of traction remained the same. A track run going completely around the machine made from six steel frames with the engine and fighting compartment located enclosed within the track run. Each frame was more compact this time, no longer the huge open rectangular frame of the first machine with four horizontal spars. This time the frames were square and made from four steel girders braced together at each corner by a triangular plate and with two rectangular ‘feet’ projecting from each side providing for additional grip on the ground. On the inside of the frame, running vertically through it, was a single steel girder connecting each of the center couplings together and connected from that was a further brace to each corner of the frame. Those four external girders, together with the triangular corner bracing, provided the ground contact area and also left a large octagonal space on the outside of the frame. Each frame segment was coupled to the preceding and following frame by a heavy steel pin in the connecting corners and also by a flexible coupling in the center, providing a very solid means of connecting each ‘link’ in this giant-sized track to each other. This massive type of track construction rendered the track impervious to damage from machine-gun fire and also providing protection for the cabin within, but also a robust system unlikely to be damaged by any obstacles it might contact on the ground. These massive frame tracks were so substantial in fact that it is hard to imagine the damage to them being caused by anything short of a direct hit by a field gun or shell.

The extremely substantial tracks of the second machine are obvious here as is the heavy riveted construction of the armored body of the tank. Source: French National Archives

An important change to the connections in this track system though was that the connections at the corners and the coupling had a small degree of lateral flexibility. Rather like the railcar coupling Boirault was so familiar with (and an expert in the design of), each frame could twist slightly against the other providing the steering movement for the vehicle. The wholly useless jacking system of the first machine was totally abandoned in favor of this design which not only ensured the crew could stay enclosed in armor, but that steering could also be effected on the move. What is unclear is exactly how this ‘flexing’ of a frame was to be carried, but as the original jacks on the floor of Machine One were hydraulic, it is a logical extraction that these jacks moved to either the rear, front or roof of the machine could be used to push on one side of a frame as it moved over it, in order to effect the movement. This system certainly worked but provided for a marginal turning movement and when this machine was later tested the radius of a turn to be 100 m.


The old machine used a pyramid-shaped cabin with the curved bottom section holding the ‘cab’, although it was open to the elements and with the engine and gearing above them. Essentially, this setup with engine-over-crew was retained on the second machine but totally gone was the tall pyramid. Instead, a new, rhomboidal shaped cabin was built with a pointed bow and stern. Constructed from heavy armor plate riveted to a steel frame, the gearing was still at the top, along with the drive chains, but the engine had been moved lower down into the rear of the machine.

Another view of the incredibly substantial tracks for the tanks and the ‘feet’ sticking out from the sides of each frame (track section). The drive gearing can be seen on top of the machine too. The two men in the photo appear to be Monsieur Boirault (left) and possibly the French Minister for War (right). Source: French National Archives.

This had the advantage of substantially lowering both the profile of the tank but also its center of gravity so it was less prone to toppling sideways. Access to this machine was by means of a large rectangular door on each side which had a curved top opening backward. In each door, a portal was fitted into which presumably a machine gun could be mounted, although no armament was specified.

Rearview of the second machine showing the drive chains descending to the engine and gearbox in the rear. The thickness of the armor is also apparent and substantial in keeping with the rest of the machine. Source: French National Archives via Vauvallier.

One photograph from trials of this machine seems to indicate a weapon mounting on the nose section of the machine which could be interpreted as the sort of weapon like a 75mm cannon required for breaking up an enemy position and later used on the Schneider CA-1, although this is speculation.

Completed second tank from Boirault showing the side door (open) and possibly a cannon mounted in the nose. Here it is negotiating the crossing of a trench at an angle. French National Library Reference #530164880

Trials and Tribulations

The spring trials of 1915 showed that the first machine had significant problems with height, speed and steering. Amendments made by the end of the year led to further trials of it in November with amendments to the steering system. These had still proven inadequate and that machine was abandoned. The principles employed though remained, and the second machine had a new steering system using the same type of ‘frame track’. When this second machine was finished, it was subjected to trials by the Army on 17th August 1916 at Souain-Perthes-les-Hurlus, in North-Eastern France. This was probably also the site of the 1915 trials of the first vehicle.

Here, despite the obvious improvements to the machine and its heavy armor and construction combined with the ability to cross a trench 1.8 meters wide, the low speed (under 2 km/h) meant that it failed to impress the Army. General Henri Gouraud (4th Army) however, was more sanguine on the matter despite the obvious problems. He was very impressed by the ingenuity of the design and the robust nature of the design. Narrower than the first machine it was still able to plow effectively through belts of barbed wire creating an avenue for any infantry to follow which was more than 2 meters wide – something which was in critical demand at the time but which was now also solved by new designs using a new robust pair of tracks.

Seen during testing in August 1916 the second Boirault tank strikes an imposing figure. The man in front is probably Monsieur Boirault himself. Source: French National Library Reference #53016523
A crowd of curious officers and men look at the mechanical marvel in front of them during tests which were presumably meant to be secret. One can only imagine what they are thinking. French National Library Reference #53016497

Postscript to the War

In a report dated 20th August 1916, Gen. Gouraud indicated he would have preferred further trials of an improved machine but these, sadly, were not to pass, and the design was abandoned by the military in favor of new tank designs which were becoming available to them. This was not, however, as thought by many historians, to be the end of the Boirault vehicles or Monsieur Boirault’s interest in this type of traction technology.

After the war was over, he continued his development with the submission of a patent in France (number FR513156) for ‘Appareil roulant pouvant etre employe comme pont automobile’ (Rolling apparatus that can be used as a motor bridge) on 1st April 1919. The patent was granted on 28th October 1920 and published the following February.

Drawings of Boiraults adventurous ideas for multiple machines forming a huge continuous bridge from French Patent FR513156(A) of 1919

The patent was nothing short of optimistic, envisaging hundreds of such frame-machines like his 1915 design with the pyramidical center acting together to form a type of rail bridge would be employed to replace missing bridges, create entirely new bridges, and even off-load full-size steam locomotives from a ship. Each frame-machine could use multiple vehicles within them to literally create a mobile moving bridge although quite how these were to actually function outside of a paper design is unclear but given that his first machine can be accepted as a ‘tank’ in some aspects, then this 1919 patent can also be accepted, by extension, as probably the most unusual tracked bridging vehicle imagined. This design was never committed to construction and it remained entirely on paper as a patent, perhaps simply just to stop someone else taking the ideas on which he had worked so hard through the difficult years of 1915 and 1916. One final note from the design is shown in Figure 8. Figure 8 shows a 12-frame machine carrying what appears to be a very heavy field piece of artillery. This enormous single-engine carrying this gun was representing a potential single engine of war or transportation replacing a series of frames using smaller engines within them. It is hard to quantify whether this additional Boirault design is a tank, a bridge, a transporter or something of all three, but certainly, the vision and ingenuity of Monsieur Boirault seemed boundless with this idea.

‘Figure 8’ from French Patent FR513156(A) of 1919 showing a huge 12-frame vehicle replacing 4 individual vehicles transporting what appears to be a large caliber gun.


The Boirault tanks were undoubtedly the most unusual tanks built and tested during the First World War and came around at a time when the technology relating to AFVs was in its infancy. The problems faced by the first machine were mostly overcome, save for speed and turning, but given the enormous progress between the two designs, it is reasonable to imagine that, given more time, this machine could genuinely have been put into production to create breaches in the enemy wire. It is perhaps sad from an engineering viewpoint that he did not continue his unique style of vehicles as tanks or attempt, post-war, an even more adventurously sized vehicle.

What is clear from his work, however, is that these machines worked. They achieved everything he had expected of them and at the time they were designed were the only machines available to the French capable of crushing the wire in no-man’s land and crossing trenches. They should not be looked upon as a failed design or something ridiculous but as a triumph of the power of engineering skills married to the imagination to come up with an innovative solution to a problem killing tens of thousands of men. Monsieur Boirault was a pioneer who helped to spur the military in France to produce tanks for the war effort. Regardless of the fact that his machines were never used in combat, the path to the design of a workable tank was a difficult one for all nations. A difficult journey in which he played his part, and should, therefore, be recognized as such, a visionary, a patriot, and engineering visionary.

Illustration of the Fortin Automobile ‘la Machine Boirault écrase barbelé’ (Eng: The Barbed Wire Crushing Boirault Machine) produced by Yuvnashva Sharma, funded by our Patreon campaign.

Specifications (Prototype No. 1)

Dimensions (L-W-H) 8 x 4 x 3 meters
Total weight, battle-ready 30 tonnes (+9 tonnes ballast later)
Crew ~2 (Commander, Gunners)
Propulsion 80hp Aster petrol engine from a Filtz agricultural tractor (petrol)
Speed 1.6 km/h

Specifications (Prototype No. 2)

Dimensions (L-W-H) 6-8 x ~3 x ~ 2-3 meters
Total weight, battle-ready 30-40 tonnes
Crew ~4 (Driver, Commander, Gunners x 2)
Speed 2 km/h
Armament est. two machine guns and one cannon
Armor ~25mm


French Patent FR513156(A) Appareil roulant pouvant etre employe comme pont automobile, filed 1st April 1919. Accepted 28th October 1920. Published 9th February 1920
Gougaud, A. (1987). L’aube de la Gloire – Les Autos-Milirailleruses et les Chars Francais pendant la Grande Guerre. Societe Ocebur
Granier, V. (1919). Les etapes successives de l’arme victorieuse: Le tank. La Science et la Vie No.44
Vauvallier, F. (2014). The Encyclopedia of French Tanks and Armoured Fighting Vehicles: 1914-1940. Histoire and Collections.
Zaloga, S. (2010). French Tanks of World War 1. Osprey Publications

WW1 French Prototypes

Delahaye’s Tank

ww1 French TanksFrance (1918)
Prototype – Models Only

Many engineering firms or manufacturers have tried and still try their hand at producing military equipment, either for lucrative contracts or as part of the mobilization of industry during war. The most widely produced AFV (Armored Fighting Vehicle) in the world, the M113, was, after all, produced by the innocuous sounding ‘Food Machinery and Chemical Corporation’ (FMC). There is a lot of sense for a car or truck maker to turn many of the same engineering skills for the production of vehicles to tanks and the French carmaker Delahaye was no different.

Sabathe and Varlet

With the First World War (1914-1919) devastating the north of France, it is no surprise that, in 1917, the Delahaye firm attempted to create their own designs to contribute to the war effort. Their chief designers, Louis-Gaston Sabathe and Amedee-Pierre Varlet, submitted a patent in March 1918 titled ‘Armement des chars de guerre’. Tanks, were, even in 1918, relatively new technology and it is not surprising that a lot of ideas for the use and development of this technology came about at this time. Sabathe and Varlet’s design, however, was very different from the existing tanks and to other tank designs of the First World War.
Their design was to use Delahaye’s own patents for caterpillar tracks filed in January 1918. These featured a relatively conventional set up of a track unit with a large diameter drive sprocket at the front and an equally sized wheel at the back which also acted as the track tensioner. Between these two large diameter wheels were three small wheels which were the load bearing portion of the system running on a thick set of metal track links. All these pieces were held together sandwiched between two triangular plates. The less conventional part of this track system was that above the level of the two large wheels was a large central pivoting mounting for the entire unit allowing it to both pivot as a single unit and around which was a chain which drove the front sprocket. This design had itself been a development of a design filed the previous January by Delahaye which had the pivot/drive for the track unit to be at the same level as the two wheels and actually connect directly to that triangular support plate. By separating the drive from this plate, the designers had neatly created a system of suspension for the track unit.

French Patents FR503169 (left) of January 1917 and FR504012 (right) of January 1918
The outline of this modified patented track unit was then featured in a second application by the firm and was specifically described in the application as being suitable for use in an assault tank. The drawing in the patent makes clear why the design was suitable for military purposes, as the vehicle body accommodated a high degree of movement making it suitable for movement over very rough terrain. On top of the flexibility of the movement which allowed the vehicle to effectively move in two halves, the track units were also shown rotating around that central pivot/drive, ensuring that the tracks would stay in contact with the ground too.

French Patent FR504013 of January 1918
With these ideas and designs at their disposal, Varlet and Sabathe continued to work on this idea, which, to function as a tank, would clearly have to have some offensive capability too. They would also expand on their track ideas to increase the off-road capabilities of their tank.
Part of this next step though meant ‘looking backward’. In July 1917, Sabathe of Delahaye had filed a patent without Varlet relating to moving assault artillery across the battlefield. This design was an unusual platform vehicle with no turret and with the field gun or artillery piece attached on a pintle mount in the middle, all surrounded and protected by and large box-shaped body with an angular front and rear. On each side were three large-diameter octagonal wheels with each face fitted with five ‘goat’s feet’ for a total 40 feet per wheel, 120 per side. As this vehicle approached an obstacle, the large platform carried above was lowered by means of a rotating boom fixed to the front axle and placed in front of the vehicle. The platform was then dropped, the obstacle crossed, and the artillery could continue its advance. This is one of the first designs for a bridge carrying military vehicle, but, although this design never progressed, the use of a non-circular wheel had shown potential to Sabathe as it could increase the ground area the wheel was in contact with improving off-road performance. Combining that idea from 1917 with the 1918 patents and a combination of polygonal wheel, and a track layer was created. This was the unorthodox triangular caterpillar wheel.

French Patent FR503609 of July 1917 showing the Sabathe designed armored trench crossing artillery vehicle

Artist’s impression of the Delhaye bridging AFV of 1917. Source: Author

French Patent FR504609 of March 1918 showing the triangular caterpillar drive wheel.

The Triangular Caterpillar

Sabathe’s ideas for polygonal wheels were combined with the work by him and Varlet for the creation of a triangular caterpillar drive unit. Although it appears to be very complicated, the system is relatively straightforward. The drive, as with the original January 1918 patents, was centrally driven via a chain from the same shaft that provided support for the unit and the axis around which it could pivot. Drive was not by chain this time, but by a toothed gear instead, and still went to a large diameter toothed sprocket wheel providing drive for the same style of heavy bodied metal track links with a flat grouser. This sprocket was fixed between a sandwich of two large triangular plates which had larger (toothless) undriven wheels at the other two corners, both of which were fitted with a track tensioning screw. All three sides of the unit were fitted with the same style of a trio of small wheels which would bear the majority of the vehicle’s load when on the ground, although, of the 9 wheels around the unit, not more than ⅓ of the track could be in contact with the ground when on flat hard ground. Sabathe and Varlet concluded their application claiming this triangular caterpillar could be used on war machines to help cross uneven and broken ground as well as trenches. Their next step was therefore logical. Combining this triangular all-terrain wheel with the flexibly coupled body from July 1917 to form a tank, offensive weapons would have to be included too.

Delahaye’s unique Tank design with triangular track system. Illustration produced by Yuvnashva Sharma, funded by our Patreon Campaign

The Tank’s Design

The design itself was a logical destination for Sabathe and Varlet who filed their tank design incorporating their ideas for tracks and vehicle in March 1918 under the title ‘Armement des chars de guerre’. This design is similar to the articulated vehicle from before, featuring a two-part body. Each section was the same basic size and shape with a roughly square body with the leading and reverse edges angled in towards the center. The rear section also sported a long cranked pair of arms extending forwards over the lead section. A large cylindrical pin then held a second set of cranked arms which curved back and down behind this first section and had a further pin fitting. The front section could, therefore, rotate sideways about this second pin as well as horizontally about the first pin. On top of the first section was a set of grooves into which another pin coming down from this second set of arms which held the first body-section in place as it rotated sideways.
These two sections could also be connected together to more tanks like this via flexible connections at the front and back of the vehicle, creating a long tank train which would be useful crossing soft or broken ground, as any vehicle becoming bogged down could be pushed or pulled by a connected vehicle either behind or in front of it respectively.
On top of this cranked arm structure was another unusual feature; an oscillating turret. This circular turret was made from a short narrow cylinder forming the body and a wider cylinder above it creating the turret itself from which projected the main gun and the whole turret was topped off with a domed roof. This body was attached to the low collar-ring attached to the cranked arms by a large pin which formed the pivot point. The pivot point allowed the entire turret to move in the vertical plane providing elevation to at least 45 degrees and up to 60 degrees although depression was restricted to -2 degrees in the field of fire by the front section of the body when firing forwards and by fouling on the cranked arm supports. The collar permitted rotation in a full 360 degrees meaning that this design could provide excellent coverage for all-road fire with the gun including the thought that this high elevation would enable it to engage flying targets. With the gun fixed in place in the turret, this meant that complex gun mountings could be completely avoided as could any weakness in the turret caused by having to allow for the gun to move. The size and type of gun for this turret was not specified in the patent except to say that it would be of an appropriate caliber to engage enemy targets including tanks, which in 1918, would have been the German A7V or captured Allied tanks. Other weapons were contained within the two body sections and included variously dispositions of 3 machine-guns, grenade launchers and small cannons. Each body section would, therefore, require at least 3 to 4 men to crew it. With at least 2 more in the turret, the vehicle would have to have a crew of at least 8 or more men.

French Patent FR504610 of March 1918.
The suspension for the design is drawn not with the unusual triangular wheels, but with the more conventional shape outline in the January 1918 patents with the pivot point lying between the two big wheels. Each section of the hull was provided with its own engine of an unspecified type which would power the two track units. Should one engine fail or become damaged, the vehicle would still be able to move and function, albeit at a limited capacity. Importantly, this design would also be able to use the patented triangular wheels, but as the pivot point was in the center of the triangle this would raise the vehicle of the ground substantially more than the system drawn in the patent.

Artist’s impression of the Delahaye 1918 Patent tank using the patented triangular caterpillar wheels. Image: Author
A photo exists of almost precisely this arrangement of triangular caterpillars on a system nearly identical to this one consisting of a two-segment body with the same cranked arm holding the pivot for one section. Between the two sections, suspended between the arms, is a turret, but strangely, this turret does not appear to have any rotation mechanism shown. It is only a model, which might explain that, but if it is missing this rotating collar, then not only does the turret appear fixed facing to the rear (assuming the front is the same as the 1918 Patent drawing), but that it is also seriously hampered in its fighting ability as it would be reliant upon the body to turn in order to aim the gun.

Model of an unknown variant of the Delahaye Tank featuring the distinctive patented triangular caterpillar drive tracks/wheels and unusual stabilization for the turret. Source: Model Archives
With the triangular wheels rotating out of sync with each other, the vehicle would end up lurching violently from left to right as it crossed any battlefield and it is perhaps for this reason why in the 1918 patent the turret is better positioned and the track units are the smaller more conventional style. Although some online sources state that this model was some continuation of the Delahaye project in the 1930s, this cannot be verified at this time due to a lack of information. It could well be a 1918 vision of what that patent design tank would look like with the triangular wheels (patented the same day) or it could be a later design.
Either way, the design was far too complex and was never adopted. By the 1930s, it would have been irrelevant anyway, as France already had the well armored and advanced Char B1 tank instead, with a much more conventional layout.


French Patent FR503169(A) filed 20th January 1917, granted 10th March 1920
French Patent FR503609(A) filed 27th July 1917, granted 21st March 1920
French Patent FR503904(A) filed 24th November 1917, granted 27th March 1920
French Patent FR504012(A) filed 5th January 1918, granted 31st March 1920
French Patent FR504013(A) filed 5th January 1918, granted 31st March 1920
French Patent FR504609(A) filed 29th March 1918, granted 19th April 1920
French Patent FR504610(A) filed 29th March 1918, granted 19th April 1920
Model Archives
Chars de France, (1997) Jean-Gabriel Jeudy, ETAI

WW1 French Prototypes

Frot-Turmel-Laffly Armoured Road Roller

ww1 French TanksFrance (1915)
Tank – 1 Built

The basis for this vehicle, like so many other early attempts at armored vehicles, was a commercial chassis. Whereas other designs used tractors or armored cars, this machine, designed by Monsieur Paul Frot, used a road roller. The machine, therefore, is not a tank or armored car, but an armored road-roller.

Why a road-roller? Well, going back to the problems of the war, it was the barbed wire which caused the greatest headaches. Troops were exposed to withering machine gun because the belts of wire made movement slow and exposed them to it. Remove the wire and the troops could get to the enemy and fight. The design of Monsieur Boirault had sought to simply flatten and crush its way through these wire belts. Other designs were about progressively cutting a path through the wire, but Monsieur Frot and Monsieur Turmel were simply going to crush it down and roll it into the mud. In this regard, their ideas were very similar to those of Winston Churchill and Maurice Hankey at around this same time, who planned to use rollers to crush down wire and the pickets holding them up, a plan which was shown to be wholly impractical and was not pursued. The French, however, were more adventurous and willing to try it, and thus, the product of M. Frot and Turmel based on a Laffly roller was born.

The Laffly road roller was a modern vehicle with a petrol engine which had been patented in 1909.

An artists interpritation of the Frot-Turmel-Laffly Armoured Road Roller


The design work on the vehicle started in December 1914 with the engineer Paul Frot at Compagnie Nationale du Nord (Northern Railway Company), although the idea for it may have been around as early as November that year. Frot wrote to the Ministry of War with his idea describing it in wildly optimistic terms as “a redoubtable war machine which from the moment it appears will strike terror in the ranks of the enemy”.
The proposal was simple – take an existing chassis of a heavy vehicle, in this case, a road roller, and turn it into an armored vehicle by covering it in armor. It was as simple as that, no armor underneath, the front roller would simply go over and pulverize the stakes holding up the wire and the armored body would protect the vehicle. Cladding the vehicle in armor was a simple process making the front and rear of the vehicle steeply angled so as not to get caught on obstacles. At the front, a curved face to the tank contained the only forward-firing weapon, a single machine gun. More weapons would be fitted too, with two more machine guns in this frontal portion to cover the sides with limited traverse. At the sides of the road roller, the armored hull swelled outwards to allow for some extra width so another machine gun could be mounted on each side. The rear matched the front with machine guns at the sides and one more at the rear too. A grand total of eight machine guns.
In the central section of the machine, the sides swelled out with angled plates and on these angled sections were large rectangular access doors, although the quality of photographs and drawings from the time do not make clear if there were two doors per side or just one, or if, indeed, both sides even had doors. Logically though, any doors would have been on the reverse face of these side sections to afford some protection for the door from the direction of enemy fire as a large door opening towards the enemy is generally not a good idea. Various other loopholes are shown in many contemporary images, although some have clearly been heavily touched up. Some were altered to show not a machine gun in the sides but a cannon instead, but the photos which have not been retouched do not show this. Inside the vehicle, platforms would be required in order for the troops manning the weapons to stand on, and despite the somewhat impractical nature of the idea, it was given approval by the Minister for War to go ahead.

Frot-Laffly armored steamroller undergoing tests April 1915. Only one machine gun can be seen, mounted in the front on the side, suggesting that the other side armament in contemporary images was added later. Source: Granier

Another image of the Frot-Laffly armored road roller showing numerous weapons and portholes not seen in the vehicle as it appears in photographs and showing 4 equally sized wheels whereas a road roller actually has only the two wheels at the back and the roller at the front. Source: Plonquet
With potentially up to eight machine guns, the crew for this vehicle would have been large, probably 10 men based on 8 gunners, a driver, and a commander. If the un-retouched photo is correct, then the three machine guns in the nose would have brought the crew down to just 5 or so, still a lot of men to fit in a small space alongside a hot engine in the middle. The vehicle, despite its size at 7 meters long, 2 meters wide, and 2.3 meters high, was surprisingly light being described at just 10 tonnes, but this does not make sense.
In 1910, for example, Laffly were offering their latest petrol-engined rollers which ranged from 5 ½ tonnes to 9 tonnes with engines ranging from 12 to 15hp, so it is reasonable to assume that a 20 hp model was more than 9 tonnes as a plain road roller before any ideas of an armored body. Given that the majority of sources give the weight of the machine as 10 tonnes, it can be assumed that the ‘10 tonnes’ is not, in fact, the complete weight with armor, but actually just the weight of the roller without armor.
Regardless of its weight though, the problem was the wheels. The rear wheels were covered in rubber for extra traction and, whilst the machine could move adequately along a hard road or paved surface, it was a road roller still. Even without the additional burden of the armor, such a machine should have been obviously impractical for travel across soft muddy ground, the sort of battlefield conditions where even horses and men could get stuck was not the place for a vehicle with all of the disadvantages of an armored car – a class of vehicle already understood to have serious off-road limitations.
On 26th January 1915, M. Frot wrote once more about the machine describing how it was supposed to work “not only in order to knock over, flatten and sever the barbed wire entanglements, but also and especially to turn it into an offensive machine of the first rank”.

Illustration of the Frot-Turmel-Laffly Armoured Road Roller, produced by Yuvnashva Sharma, funded by our Patreon Campaign.

Tests and Conclusion

Once built, this ridiculous machine was tested in the grounds of the Corpet and Louvet Factory at La Courneuve, North of Paris, on 28th March 1915 and performed extremely well. The ground was hard and to the shock of no one, this giant road roller easily crushed the steel pickets and wire entanglements in front of it but this was tested under ideal conditions. No enemy fire, no soft ground, ditches, trenches, or obstacles to cross. At this point, the military authorities finally saw sense and dumped the idea as the machine was clearly impractical for the conditions at the front. It should never have gone as far as it did, but perhaps in the eagerness to test new ideas with the war raging, the French can be forgiven for this extravagance. It showed that wire entanglements could be crushed and mechanized vehicles could do the job. Wire did not have to be cut to be rendered useless for infantry attacks and importantly, vehicles based on commercial equipment like this road roller were not what was needed. Tracks, not wheels or rollers, were going to be the form of traction for this modern war.
Presumably, following the abandonment, the vehicle was dismantled and the Laffly roller returned to its original duties, ending one of the least realistic ideas to have seen the light of day in WW1.

Frot-Turmel-Laffly armored roller during testing in March 1915 at the Carpet and Louvet Factory. The background has been deliberately altered to hide the buildings in the background, presumably for secrecy reasons. Source: Vauvallier


Dimensions (L-W-H) 7 x 2 x 2.3 meters
Total weight, battle ready 10 tonnes
Crew ~10 (Driver, Commander, up to 8 machine gunners)
Propulsion Laffly Type LT 4.82 litre 4-cylinder 20hp petrol engine
Armament Up to 8 machine guns
Armor est. 7 mm
Total Production 1


Chars Francais, Frot-Turmel-Laffly
Blanchard, A., Drowne, H. (1911). Highway Engineering: 2nd Internal Road Congress Brussles 1910. Chapman & Hall Ltd. London
British Patent GB21571 ‘An improved motor driven road roller’. Filed 21st September 1909, accepted 30th June 1910
French Patent FR401592 ‘Rouleau compresseur automobile’. Fired 2nd April 1909, accepted 31st July 1909. Published 3rd September 1909
Gougaud, A. (1987). L’aube de la Gloire – Les Autos-Milirailleruses et les Chars Francais pendant la Grande Guerre. Societe Ocebur
Granier, V. (1919). Les etapes successives de l’arme victorieuse: Le tank. La Science et la Vie No.44
Ogorkiewicz, R. (2015). Tanks: 100 years of evolution. Bloomsbury Press, London
Plonquet, E. (19__ ). Rouleau Cuirasse: Char d’assaut et tank.
Vauvallier, F. (2014). The Encyclopedia of French Tanks and Armoured Fighting Vehicles: 1914-1940. Histoire and Collections.
Zaloga, S. (2010). French Tanks of World War 1. Osprey Publications

Tanks Encyclopedia Magazine, #3

Tanks Encyclopedia Magazine, #1 Republished

The first issue of the Tank Encyclopedia Magazine has been remastered and rereleased. It covers vehicles ranging from the French WWI Frot-Turmel-Laffly Armoured Road Roller up to the Salvadoran Cold War Marenco M114 converted vehicles. The star of this issue is a full article on the Improved Protection version of the famous M1 Abrams – the M1IP.

Our Archive section covers the history of the Mephisto A7V tank, the only one of its kind that still survives to this day in Queensland museum in Australia.

It also contains a modeling article on how to create Weathering and Mud Effects. And the last article from our colleagues and friends from Plane Encyclopedia covers the story of the Sikorsky S-70C-2 Black Hawk in Chinese service!

All the articles are well researched by our excellent team of writers and are accompanied by beautiful illustrations and photos. If you love tanks, this is the magazine for you!
Buy this magazine on Payhip!