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Barnes Two-Man Heavy Tank

United States of America (1938)
Heavy Tank – None Built

Lt. Colonel Gladeon M. Barnes from the US Army’s Ordnance Department casts a long shadow over tank development in the USA in the period around the start of WW2. Barnes was an interesting man, but some of his ideas and designs were demonstrative of a disconnect between his thinking and military reality.

One such example came in 1938 with the idea for a small heavy tank armed with a single machine gun. Quite what role such a vehicle was meant to fulfill is hard to imagine years after other users of such vehicles had already accepted the serious inherent limitations of a similar type of vehicle.


Somewhat oddly, the inspiration for this idea came from the Spanish Civil War. Section G-2 (the department responsible for Intelligence in the US Army) examined that conflict for lessons in a report titled ‘Tank Lessons from the Spanish Civil War’. They concluded that tanks were too poorly armored, used in too few numbers, and that they were not maneuverable enough.
In that war, the primary tanks being used were the German-supplied Panzer I, the Italian CV.3 series light tank, and the Soviet-supplied T-26 light tank. During that war, as G-2 correctly pointed out, tanks tended to be used in small numbers or alone and both the CV.3 series and T-26 had thin armor, around 14 to 15 mm maximum, meaning both were just bulletproof.

The T-26 had an advantage over the CV.3 in the addition of a turret-mounted weapon, whilst the CV.3 was stuck with its only armament in a mounting on the front left of the hull facing forwards. Neither tank was able to demonstrate much speed even though the CV.3 was faster, just under 30 miles per hour (48 km/h) compared to just under 20 miles per hour (32 km/h) for the T-26, although the overall effect was slight. Both tanks were too slow, both suffered from narrow tracks and a relatively underpowered engine. Any reasonable and objective assessment of the use of tanks in the Spanish Civil War would reflect this.

The Italians, for example, understood from the conflict the severe limitations of the CV.3 for tank vs tank combat and undertook work on turreted light tanks with some urgency. The Germans and Soviets likewise looked and learned. Why then did the US see a solution lying in a vehicle with the same sort of layout as the CV.3 but with less armament is difficult to comprehend.

The outline of Barnes’ concept for a 2-man heavy tank.(Source: Armor Magazine)

The design

Barnes’ concept was for a small light tank, just 7 US tons (6.35 tonnes) or so and just 11 feet (3.35 m) long. For reference, the Italian CV.3 was less than half the weight, shorter, narrower, and lower, and the Soviet T-26 was heavier and slightly longer, wider, and taller.

With a crew of just two, both men would have their work cut out for them. One man had to drive the tank and operate its radio, almost certainly sat on the left just like on the Light Tank T3. The other crew member would have to both command the tank and operate the armament and would sit on the right, alongside the other man. This is a very similar arrangement to the Italian CV.3, except the crew position/roles were reversed. It could be considered that these reductions in size and capability were, in fact, simply the means to get the most tank possible for the least money. However, here Barnes trips-up once more. He provided a cost estimate of US$20,000. In 1938, US$20,000 was a huge sum of money, equivalent to over US$350,000 in 2020 values, or roughly half the cost of a far more potent and useful Sherman tank.

Comparison between Barnes’ design and the primary Spanish Civil War Tanks

The 2-man heavy German Pz.I Italian CV.3 Soviet T-26
Crew 2 2 2 2
Armament 1 x 37 mm / 1 x .30 cal MG 2 x 7.92 mm machine guns 2 x 6 mm machine guns 1 x 45 mm & 1 x 7.62 mm MG
L / W / H
11’ x 6.5’ x 4.5’
(3.35m x 1.98m x 1.37m)
4.02 x 2.06 x 1.72
3.03 x 1.4 x 1.2
4.65 x 2.44 x 2.24
Weight 7 tons (US)
(6.35 tonnes)
5.4 tonnes ~3 tonnes 9.6 tonnes
(off road/on road)
20 mph / 35 mph
(32 km/h / 56 km/h)
25 km/h / 37 km/h 42 km/h 42 km/h
F / S / R
(38 mm)
7 – 13 mm 14 / 8 / 8
15 / 15 / 15
Note No turret Turreted No turret Turreted

The Armament

The drawing of Barnes’ vehicle shows a single machine gun and the annotation states this to be a single .30 caliber (7.62 mm) weapon with 60 degrees of traverse, presumably 30 degrees to each side. An alternative armament was also proposed, a 37 mm gun. Once more, this was to be mounted in the front, seriously limiting its potential effectiveness. On top of this failing, operating a gun is a lot of work to load, aim and fire and, perhaps because of this, Barnes did propose that it could be automatically fed. Thus, the commander would have to ‘only’ command the tank, aim and fire the gun. Even so, the tank, limited by the traverse of its gun, would still be inferior to the Soviet T-26.


If the CV.3 and T-26 were unsuitable, with armor only 15 mm at most, then the goal would be to have more, presumably to make the tank protected against automatic cannon fire such as the potent 20 mm Breda cannon which was a proven armor-killer in Spain. It would also mean anti-tank rifles would be less useful against tanks, so more armor was not an unreasonable goal. Barnes wanted up to 1.5 inches (38 mm) of armor on this small heavy tank. For the purposes of reference, the Czech LT vz. 35 (better known as the Panzer 35(t) in German service in WW2), a tank which is possibly the preeminent and most modern turreted tank of the era, had just 25 mm across the whole front. What Barnes was indeed proposing was a tank the size of the diminutive American Light Tank T3, a little larger than the Italian CV.3 light tank, but with armor heavier than most of the tanks then in European service. All that, just to carry a single and rather limited machine gun, a task the even smaller CV.3 did more effectively with two machine guns mounted together.

tiny Light Tank T3
With a soldier for scale, the tiny Light Tank T3 shows really just how small it was. (Source: Hunnicutt)


The speed and agility of the vehicles in the Spanish Civil War were seen as a failure because they were insufficient. Therefore, Barnes should have been looking for a vehicle able to exceed the speed of the CV.3. Instead, he managed to make a vehicle which even under ideal circumstances was larger, heavier, and slower.

The power to weight ratio of this design was to be 20 to 25 horsepower per ton and, with an estimated 7-ton (6.35 tonnes) weight, that would mean an engine of 140 to 175 hp. Ideally, this would mean a top speed of 20 mph (32 km/h) on a slight slope and 35 mph (56 km/h) on a road. On paper, this all sounded good, but paper-designs are like that and a magic engine can be produced from thin air with imaginary performance. When the design meets reality, things change and this is exemplified by the Light Tank T3.

Although Barnes did not specify which engine was going to be used, the Light Tank T3, produced two years earlier in 1936 gives a good idea of the problems. Both vehicles clearly use a pair of volute-sprung bogies, each with two wheels and a front-mounted drive sprocket meaning the transmission was in the front. The Light Tank T3 is very similar in size, suspensions, armament, and appearance to Barnes’ idea and was fitted with a 221 cubic inch (3.62 litre) Ford V-8 engine. Despite being slightly over 3.54 US tons (3.21 tonnes), this vehicle had half of the armor Barnes was proposing and yet had the same top speed. The Light Tank T3 was the same size as Barnes’ idea, with half the armor and half the weight, and yet the same desired performance meaning whatever engine Barnes was considering would have to be significantly more powerful and yet fit in the same space as available in the T3. This was no small order, although the Combat Car T5 of 1933 had managed to cram a 235 hp air-cooled Continental R-670 radial petrol engine inside, all for 6.29 US tons (5.71 tonnes), albeit with armor around just ½” to ⅝” thick (12.7 to 16 mm).

US Light Tank T3 of 1936
US Light Tank T3 of 1936. (Source: AGF)

The closest vehicle, perhaps to Barnes’ idea, was not the Light Tank T3, but the Light Tank T6. Built in 1939, one year after Barnes’s 1938 concept, the Light Tank T6 departed from the suspension of the Light Tank T3, using just a single 2-wheel bogey with a volute spring and the large on-ground trailing wheel at the back along with a separately sprung half-bogey. Once more, the driver was to be on the left in another two-man tank but this vehicle was not armed at all. With armor up to 1” (25 mm) thick and weighing in at 9.75 US tons (8.85 tonnes), the Light Tank T6 was roughly the same size and gives a good idea of a potential power plant for Barnes’s tank, namely a pair of 8-cylinder Buick petrol engines. However, even so, it was more than 2 tons heavier and still had armor no thicker than 1” (25 mm) and, importantly, no armament. Comparing Barnes’ idea to both Light Tanks T3 and T6 shows how unrealistic it really was.

US Light Tank T6
US Light Tank T6. (Source: AGF)

Comparison between Barnes’ design and the Light Tanks T3 and T6

Light Tank T3 The 2-man heavy Light Tank T6
Date 1936 1938 1939
Crew 2 2 2
Armament 1 x .30 cal MG 1 x 37 mm / 1 x .30 cal MG unarmed
L / W / H
11.25’ x 6.75’ x 4.5’
(3.43m x 2.06m x 1.37m)
11’ x 6.5’ x 4.5’
(3.35m x 1.98m x 1.37m
Approx. 11.25’ x 6.75’ x 4.5’
(3.43m x 2.06m x 1.37m)
Weight 3.54 tons (US)
(3.21 tonnes)
7 tons (US)
(6.35 tonnes)
9.75 tons (US)
(8.85 tonnes)
Engine Ford V8 Petrol unstated Twin Buick 8-cylinder Petrol
(off road / on road)
? mph / 35 mph
(? km/h / 56 km/h)
20 mph / 35 mph
(32 km/h / 56 km/h)
? mph / 30 mph
(? km/h / 48 km/h)
F / S / R
¼” to ⅜”
(6.35 to 9.53 mm)
(38 mm)
⅜” to 1”
(9.53 to 25 mm)
Note No turret No turret No turret


It is hard to see any merit in Barnes’ idea. The armor certainly would have provided excellent protection from the relatively small caliber weapons then in service on a lot of tanks, but those were the previous generation. Against a 37 mm anti-tank gun, like the type used in numbers in Spain to good effect, even 38 mm of armor was not going to be much help, although it would certainly have made the little tank impervious to infantry which did not have access to a cannon. What then was Barnes’ really proposing? A small lightly armed and heavily armored tank may have some utility against infantry but, with the only armament in the front it would, as the Italians found to their cost, prove untenable. If, however, Barnes was really considering a small tank destroyer then why bother with the armor at all. Concealment and maneuverability would have been of far more use and he could reasonably have mounted the gun on top in an open-setting for a wider arc of fire and more space to carry ammunition.

Both ideas were also stymied by the selection of just two crew. There was simply too much for two men to do in combat, so a slightly larger chassis would also have allowed a third or fourth man to operate the gun, but would also have severely increased the weight and decreased the mobility.

Finally, Barnes’ concept of mobility was flawed. There was no way he was going to get even more armor and an automatic 37 mm anti-tank gun into a vehicle no bigger than the 9-ton Light Tank T6, along with a larger engine and still have the same performance. Likewise, he could not have allowed the weight to go over 7.5 tons (6.8 tonnes), as this was the limit set in 1933 by the Secretary of War for light tanks, suggesting a reason behind the ‘heavy’ part of the name, and that is before the eye-watering price-tag for the vehicle was considered.

Illustration of Barnes Two-Man Heavy Tank illustrated by Yuvnashva Sharma and funded by our Patreon campaign.

Barnes 2-man Heavy Tank specifications

Weight 7 tons (6.35 tonnes).
Crew 2 (Commander/gunner, and driver/radio operator)
Propulsion Type unknown, 140-175 hp desired
Desired Speed 20 mph off-road / 35 mph on road (32 km/h / 56 km/h)
Trench Crossing 4 feet (1.22 m)
Armament 37 mm gun or .30 caliber machine gun
Armor up to 1.5 inches (38 mm)
Total production None


Bellinger, J. American Hetzer. AFV news Magazine 37(2)
AFV Data Series
Crimson, F. (1992). US Military Tracked Vehicles. Crestline, USA
United States Army. The General Staff: Its Origins and Powers
Christie, J. (1985). Steel Steeds Christie. Sunflower University Press, Kansas, USA
AGF Board. (1947). Development of Armored Vehicles Vol.1: Tanks.
Hunnicutt, R. (1992). Stuart. Presidio Press, USA

4 replies on “Barnes Two-Man Heavy Tank”

This is an interesting article, but I have some remarks and a question.

The table with the data for the T-26 shows incorrect speed and crew.

Any idea why no one suggested the M2 .50 rather than the M1919 .30? If there could be made room for (presumed) a M5 -37mm then it shouldn’t be a problem to have a heavy machinegun as an inbetween.

1x M1919 .30 would in practice be a better weapon than the 2x M30 Breda for the L3/33 or later 2x M38 Breda for the L3/35. It offers more consistant fire vs the 20 strip & 24 mag systems of the Breda guns.
It also fires at a higher rate, though it’s a single mount.
The fact it even HAS a radio would also give it an edge over the L3-serie

I also want to add that 38 mm of armor for pre-WW2 vehicle is respectable. Authors in this site often undervalue armor values, but in reality Germans and many other nations did not had any or few high penetrating anti tank guns at the start of WW2. Pak 36 in this case can beat 38 mm of armor then under 500 meters which is quite respectable for such a small vehicle. Comparable anti tank guns also had similar penetration ranges around 500 meters which allows this tankette to neutralize enemy anti tank defenses with its machine gun or cannon while being able to resist incoming fire.

In addition, Sherman had costed more than twice that this vehicle costs despite having tremendous advantage of economies of scale. It is always difficult to compare what is expensive in war and we should rather look at what shortages we have and what is effective. If soldiers can make an effective usage of weapons platform when generally it is worth the money.

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