"Based on combat experience of using M3 medium and M3 light tanks in the 153rd Tank Brigade, and also experience from June 24th to August 31st, the following can be said. These tanks can be used to break through a defensive line, even in the presence of dense enemy anti-tank fire. The presence of powerful armament and robust armour allows for successful combat with enemy tanks and infantry. During pre-battle use and combat use in the brigade, the light and medium tanks showed the following strengths and weaknesses:
- Armour. The front and turret armour stands up well against hits from HEAT shells. All hits to the front of the tank, especially the medium tanks, fail to penetrate the entire thickness of the armour. As a rule, the shell melts the first layer, and then gets stuck. As such, it fails to penetrate into the tank. The side armour, due to its insufficient thickness, is easily penetrated by AT guns, and the top armour can be penetrated by mortars. A drawback of the turret design is that if it is hit by a mortar shell, it jams. There were also instances of the gun mantlets of 75 and 37 mm guns jamming.
- The cannons and machineguns are sufficiently powerful, but the Browning machinegun has several design defects. These defects result in casings tearing during automatic fire, which jams the machinegun. The cannons work flawlessly. Crew workspaces in the tank are mostly comfortable. Shells for the 75 mm gun are placed well. Shells for the 37 mm gun are placed inconveniently, as some of them are placed in the main fighting compartment. When all 37 mm shells in the turret are used up, it is impossible to get more shells when the tank is moving. This can only be achieved with help from the 75 mm gun loader, which reduces the rate of fire and makes his job very difficult.
- Tank components. Having used the tanks for two months, during long 110-160 km marches on difficult terrain, it can be seen that the engine group works flawlessly. "Continental" motors on light tanks had cases of articulated connecting rods tearing off, which indicates a design flaw. There have been cases of hoses that connect the air intake and carburettor being damaged. Transmission components mostly behave well, except in two cases of the main friction clutch and 3rd adn 4th gears getting jammed on light tanks. There were two cases of road wheels getting jammed in their bogies (in light tanks). The double differential makes braking reliable. All components are placed conveniently from a maintenance perspective. However, the engine is placed inconveniently for adjusting valves. When performing this operation, it is necessary to remove the upper and lower rear armour plates. Over two months, the controls worked flawlessly, and did not require adjustment. The cooling system works well in the summer, and guarantees proper operation of the engine (no overheating was detected).
- The use of high quality gasoline results in immediate ignition when hit by incendiary shells.
- There are not enough observation devices, and communication inside the tank is poor. The radio works flawlessly.
- Observation devices and sights break when the armour is hit by shells or bullets, even when this happens a significant distance away from the device.