Monday 2 September 2013

Mobility Tests of Lend-Lease and Foreign Tanks

Aside from testing the gun and armour of the captured PzIII and Pz 38(t) tanks, the Soviets also tested their mobility against the Valentine, Lee, and Stuart tanks. The description of the trials and their results can be found in CAMD RF 38-11355-817.

"The following tanks participated in the trials:
  • American tank M3 Medium (M3 Lee)
  • American tank M3 Light (M3 Stuart)
  • Canadian tank Mk III (Valentine VII)
  • German tank PzIII
  • Czechoslovakian tank Praga TNG-S 38t (Pz 38(t))
Captured PzIII and 38t tanks were repaired at the proving grounds workshops before the trials. English Mk III tanks with AEC engines and Mk-IIa with Leyland engines could not participate, as the proving grounds had no functional tanks of those types."

The tanks were tested across 1000 km of various terrain types. Their maximum and average speeds, fuel efficiency, operational range, fording depth, maximum tilt, and swamp crossing capability were tested.

The terrain tests were done in the following conditions:

"Road: stone and gravel, section of road between Kazan and Lyshevo.
Dirt road: field and forest of various quality, from dry sand to moist clay.
Off-road: last year's plowed field, dry grass plain, silty sand."

The resulting average speeds on this terrain were as follows. Speeds are given in kilometers per hour.
  • M3 Lee
    • Maximum: 34
    • Stone road: 26
    • Dirt road: 17
    • Off-road: 12
  • M3 Stuart
    • Maximum: 60
    • Stone road: 38
    • Dirt road: 29
    • Off-road: 20
  • Canadian Valentine
    • Maximum: 26
    • Stone road: 25
    • Dirt road: 18
    • Off-road: 16
  • PzIII
    • Maximum: 45
    • Stone road: 35
    • Dirt road: 25
    • Off-road: 20
  • Pz 38(t)
    • Maximum: 30
    • Stone road: 25
    • Dirt road: 16
    • Off-road: 13
A remark is made, regarding the Valentine: "Despite its low hp/ton and maximum speed, the tank has a relatively high average speed, thanks to a fortunate construction of its gearbox and high quality of the GMC diesel engine."

Fuel efficiency during mobility tests

Next, the tilting tests. The results were as follows:
  • M3 Lee
    • Maximum slope: 30 degrees, limited by track traction
    • Maximum tilt: 25 degrees, limited by track slipping off
  • M3 Stuart
    • Maximum slope: 30 degrees, limited by track traction
    • Maximum tilt: 35 degrees, limited by tank falling over
    • Comments: "The tank could climb a steeper slope with tracks that have better traction. Adding 15 spurs per track link did not help with traction. Instead of slipping, the tracks dig through the ground near the rear of the tank." 
  • Valentine
    • Maximum slope: 32 degrees, limited by track traction
    • Maximum tilt: 26 degrees, limited by track slipping off
    • Comments: "The tank could climb a steeper slope, but is limited due to its track traction."
  • PzIII
    • Maximum slope: 35 degrees, limited by track traction
    • Maximum tilt: 32 degrees, limited by track slipping off
  • Pz38(t)
    • Maximum slope: 30 degrees, limited by track traction
    • Maximum tilt: 25 degrees, limited by track slipping off
Next, the tanks' ability to ford a river was tested. The river was 45 meters across, maximum 1.4 meters deep, 0.2 m/s current. River floor is sandy. The right shore is gradual, and sandy. The left shore is a 15-20 degree slope, and is composed of silty dirt. The tanks crossed the river from the right shore to the left, turned around, and came back.

"M3 Medium: the tank crossed the river in second gear, with maximum depth of 1400 mm. The tank crossed the river easily. The tank fills up with water slowly, due to the current caused by the tank's movement preventing the water from entering through a cooling vent in the rear of the tank. It is concluded that the M3 Medium can cross a river deeper than 1400 mm. When the tank attempted to exit on the opposite shore, the engine was not powerful enough, and it stopped, tilted back 20-25 degrees. The engine compartment was flooded and the engine stalled. The cause of this was the fact that the water went over 1500 mm relative to the bottom of the tank. The tank was towed out of the river by a Voroshilovets tractor."

M3 Lee tank, stalled after attempting to exit the river.

"The M3 Light tank crossed the river in third gear, in both directions, with a maximum depth of 1400 mm. While attempting to exit on the left shore, the tank was stuck in the silty dirt. The tank reversed 8-10 meters, turned, and exited on a section with better ground. Reversing and maneuvers in the water did not lead to flooding of the tank, due to the speed at which they were carried out, possible in this tank due to high hp/ton, and due to the fact that the engine vent is located not vertically, like on the M3 Medium, but horizontally, protected by an air pocket. The tank confidently crossed the 1400 mm deep river, turned around, and crossed it again."

M3 Stuart tank, crossing the river once again, after a successful crossing.

"The Mk III Canadian [Valentine] tank crossed the river in third gear, with a maximum depth of 1400 mm. While attempting to exit on the opposite shore at an angle of 40-45 degrees, the tank was stuck in the silty dirt. In an attempt to move forward, it slid to the right. In order to position the tank perpendicularly to the shore, the tank backed up 15 meters into the river, at a depth of 1400 mm. As a result of moving backwards, the engine compartment flooded through the air filters, and the engine stopped. The reason for flooding was the tank moving in reverse. The Canadian Mk III tank confidently crosses a river 1400 mm deep. Despite the relatively low position of the air filters, the tank takes on water very slowly, due to the high speed achieved by the tank. The tank was towed out of the river."

Valentine tank crossing the river at its deepest point.

"The PzIII was crossing the river in second gear after submerging 1300 mm, the water flooded the engine compartment. The engine stalled. The tank was towed out of the river."

PzIII at 1200 mm, shortly before getting flooded.

"The 38t tank crossed the river in second gear. The tank submerged to a depth of 1350 mm, after which the water flooded the engine compartment, and the engine stopped. The tank was towed out of the river. 

Pz 38(t) crossing the river.

Next, the swamp trial. Here is a description of the swamp: "The bottom was an old river, covered in 1.2 meters of turf, with thick swamp grasses, and some water on the surface. The swamp is safe for a person, but not for a heavy animal, like a cow or a horse. It is impassable by wheeled vehicles of any kind. The swamp is 100 m in length.
Before trials, it rained for a day. All tanks crossed a fresh section of the swamp. The tanks crossed the swamp twice, once in each direction. No turns or gear changes were performed in the swamp."

"The M3 Medium tank crossed the swamp in first gear. After 30 meters, its right side started to submerge. An attempt to right the tank was fruitless, the tank did not respond to controls, and kept turning right. After several more meters, the left track lost traction, and the tank stopped, 480 mm deep in the swamp, tilted by 20 degrees. Upon an attempt to reverse, the tank dug itself to 600 mm. After a log was tied to the tracks, the right track snapped. The tank was towed out of the swamp by two heavy tractors after the right track was repaired.

M3 Lee crossing the swamp.

"The M3 Light tank crossed the swamp in third gear, at a maximum depth of 320 mm. It crossed the swamp twice, in either direction, each time in a fresh place. Upon crossing through the same place, the tank sunk 450 mm into the swamp 55 meters in, lost traction of one track, and got stuck. The tank could reverse out of the swamp with the help of a tractor."

M3 Stuart stuck in the swamp on the third pass, while attempting to cross through a previous crossing. The tank tilted 12 degrees, and the right track lost traction.

"The Mk III Canadian crossed the swamp twice, in second gear, submerged to a maximum of 400 mm. Both crossing were across fresh sections of swamp. The next pass led the tank into a previous crossing 80 meters into the swamp. After traveling several meters through its old tracks, it sank 420 mm into the ground (the size of its clearance). The tank could independently leave the swamp after a log was tied to its tracks. 

Valentine tank stuck in a swamp while attempting to cross through its own tracks. 

"The German PzIII tank was crossing the swamp in second gear. After traveling 50 meters, it sank 400 mm, and was stuck due to tracks losing traction. After an attempt to back out, the tank sank further. The tank could not back out of the swamp with logs tied to its tracks, as it lacked the engine power to do so. The tank was dragged out of the swamp with a Voroshilovets tractor."

PzIII stuck in its initial attempt to cross the swamp.

"The 38t tank crossed the swamp several times each way, each time in a new place, in second gear. The maximum depth was 280 mm."

Pz38(t) crossing the swamp.

Here are some excerpts from the conclusions (the majority of them are self-evident and uninteresting).

"Imported and captured tanks have a much lower range than the T-34 and T-70. This must be kept in mind when using them together. The difference in speeds and ranges limits the use of these tanks to certain combat roles, and, in several cases, means that combined use is impossible.
Despite their relatively high hp/ton, American tanks cannot climb hills due to poor track traction. In this, American tanks are worse than the Canadian tank and both German tanks.
Watertightness of the hulls is irrelevant when crossing rivers 30-50 m wide. The water does not enter the tank rapidly enough to reach air filters and electrical systems.
When crossing a swamp, keep the following in mind:
  • Do not stop
  • Do not follow the path of a tank that crossed previously
  • Do not turn
  • When an American tank is stuck, do not tie a log to its tracks to avoid tearing
The size of the M3 Medium allows for transport of up to 10 soldiers with PPSh submachine guns. When this many soldiers are in the tank, it is possible to fire from all of the tank's weapons. Based on this, we deem it possible to recommend the use of an M3 Medium as an APC."


  1. Checkmate, Commies! The first IFV in the world was built by the good ol' USA during WWII, not by the USSR in the 1960s!

    Also, and on a more serious note, PzIII is proven as the best German tank once again.

    1. Well, but the Americans apparently never even noticed their tank can be used as an IFV. Does it still count? :)

    2. The idea of using the "M3Lee" as an ersatz proto-IFV is certainly creative and interesting, but one has to wonder about egress in combat conditions...

      I get the impression the Soviets didn't pursue the experiment either. :/

    3. The M3 Lee does have those side hatches.

  2. M3 Stuart with applique armor is best tank of all, though

  3. God, that photo of the Valentine in the river is terrifying.