At the end of the level you are instructed to use the MG-42 machine gun. Instead of doing that, kill the Nazi on the MG-42 from the ground, then hold off the enemy for about one minute and thirty seconds. Run up to use the MG-42. The SMG that the Nazi had should have disappeared. Use the gun until the game says, "Captain Richards and Private Thomas have been killed in action", then run down the stairs and walk over the dead soldier's Thompson. Note: Make sure you do not already have an SMG before picking up the Thompson or you will just get the ammunition.