Infantry tractor – 3 prototypes
The early 1930s were marked by the worldwide popularity of the tankette concept, which produced a variety of vehicles used in sometimes quite radically different manners across most major industrial powers of the world. The Citroën P28 original prototype was one of the more original derivatives of this design. Designed to serve as an infantry tractor, it used a half-track configuration with Kégresse suspension, which makes it a quite interesting and original design. While not adopted as an infantry tractor, with the more traditional fully-tracked Renault UE being picked, it became an interesting half-track cavalry armored car.
In the wake of the Carden-Loyd
In 1928, production of the British Carden-Loyd Mark VI tankette began. The result of several years of experimentation on one and two-man turretless armored vehicles, this British tankette was a 1.5 ton heavy vehicle with a two-men crew. A novelty on the international market, which was relatively stagnant and dominated by the WW1-era French Renault FT, the Carden-Loyd seemed to offer new possibilities as a lighter and cheaper armored vehicle.
The potential was not lost on France and, in June and July 1930, two Carden-Loyds were tested at the Centre des Essais de Véhicules (Vehicles Trials Center) of Vincennes. Those trials had been conducted at the initiative of engineer Edgar Brandt. Brandt was a prolific artillery designer, responsible notably for the Brandt 27/31 81 mm mortar, an evolution of the British Stokes that would, in turn, be adopted, modified, and/or copied by virtually every major and many minor military powers of the 1930s. It is reported two different Carden-Loyds were tested, one of a “light” and one of a “heavy” model. The light one could be outfitted with a machine-gun and used as a small combat vehicle, while the heavier one was tried as an armored tractor with a tracked trailer, with the purpose of carrying the Stokes-Brandt mortar and ammunition.
The Type N program
The trials of the two Carden-Loyd vehicles proved influential in the French Army’s infantry services. On October 7th, 1930, a set of specifications was issued for a new type of vehicle. These would be véhicules blindés de ravitaillement de l’infanterie, or armored infantry supply vehicles. This set of specifications was given the denomination of “Type N” a few weeks later. The Type N specifications requested vehicles with a maximum height of 1.10 m, able to carry a load of 950 kg, typically a mortar or heavy machine gun with ammunition, crewed by two men, able to reach 35 km/h, and with an autonomy of five hours.
Projects from three different companies were ordered to be built as prototypes. The orders covered six prototype vehicles, trailers to be used by these vehicles, as well as larger trailers on which the vehicles could be carried on, towed by a truck. The first company to receive orders was Latil, which produced a design created by Brandt and Vickers-Armstrong, the makers of the Carden-Loyd. The Latil design was very similar to the original British vehicle, and one of the six prototypes was actually imported from Great Britain. The second company was Renault, generally speaking, the giant of the French armored vehicles industry in the era, which produced the UE, a small entirely tracked tankette, obviously inspired by the British Carden-Loyd but still a new design. Finally, Citroën produced the P28, a vehicle far more different from the British tankette that inspired the Type N program
Citroën’s infantry tractor
Citroën’s military vehicles of the 1920s were almost systematically fitted with the Kégresse track system. This system consisted of tracks that, instead of separate metallic interlocked parts, were instead a unitary, flexible belt. It had been created by French engineer Adolphe Kégresse whilst he was based in Imperial Russia, from 1905 onward. In 1919, Kégresse returned to France and was hired by Citroën. From then on, his track systems were featured on a large number of military vehicles, often in a half-track configuration, including artillery tractors and armored cars such as the AMC P16 (designed by Citroën but produced by Schneider) and even some Renault FT light tanks.
The vehicle presented by Citroën to match the Type N specifications was no exception to the rule. It was a small half-track with two wheels at the front used for steering and powered Kégresse tracks at the rear. These had a large front sprocket and a single bogie holding two road wheels as well as a large rear trailing wheel. A notable feature of the Citroën vehicle was that it was crewed by only one man, who sat at the front-left of the vehicle, under an openable 6 mm-thick armored hood with vision hatches on the sides. The engine was to his right; the rear of the vehicle was unarmored and featured a storage bin where weapons or ammunition would typically have been carried. The front of the P28 featured two distinctive round headlights. No armament was fitted, as the vehicle was merely intended to transport arms and ammunition under minimal protection, not to actively fight.
The engine used was a Citroën C4 4-cylinder, 72×100 1,628 cm3 engine with an output of 30 hp. This gave it a maximum speed of 39.5 km/h on-road, without a trailer. It should be noted that, when the order for prototypes was placed by the French military, the production of three half-tracked vehicles and three fully tracked ones was requested. The tracked version never left the drawing board and even its design remains unknown as of today.
Three prototypes were manufactured by Citroën, registered as 35248, 35249, and 4016-W1. The first prototype began its trials at Vincennes on 24th July 1931 and continued trials there until the 29th. The two other prototypes were delivered to the training grounds along with their trailers on July 31st of the same year. The trailer that had been designed by Citroën was wheeled, unlike the Renault UK trailer of the UE, which was tracked.
The vehicles generally performed quite poorly during those trials, with complaints being addressed to Citroën. Notably, the vehicle’s cooling left a lot to be desired, with risks of overheating the engine. There was no system for the driver to detach the trailer without leaving the vehicle, which was both impractical and potentially dangerous under fire. The French Conseil Consultatif de l’Armement (Consultative Council of Armament) was pushed to make a choice between the different vehicles in October 1931. While its trials had not been without flaw either, the more conventional Renault UE was adopted by the French military, cutting short the P28’s life as an infantry tractor, though not as a military vehicle in general.
Conclusion – a future in the cavalry
Despite the rejection of the Citroën P28 infantry tractor, it did see further evolution thanks to interest from the cavalry, which considered the vehicle’s potential evolution into a light reconnaissance armored car, leading to at least one of three prototypes being converted to mount a turret instead of the storage bin, and the order of 50 armored car variants of the P28 featuring a centrally-mounted turret in October of 1931.
As for the infantry tractors prototypes, their fate beyond 1931 is unknown. It is quite likely they ended scrapped, if not by the French in the 1930s, then by the German occupiers during the Second World War.
Whilst Citröen’s proposals were not adopted, they remain the most original vehicles offered to the French Army as part of the Type N program. In comparison, the Latil-Brandt vehicle was little more than a copy of the original Carden-Loyd, and the Renault UE took a lot of inspiration from the British vehicle, particularly suspension-wise.
Tout les blindés de l’armée Française 1914-1940, François Vauvillier, Histoire & Collections éditions,
Les matériels de l’armée Française: Les automitrailleuses de reconnaissance, Tome 1, l’AMR 33 Renault, François Vauvillier, Histoire & Collections, 2005