Chevalier

If you're talking about where you enter the cannon (huge train looking thing) go and kill the germans inside of it by climbing the ladder behind the huge thing and knock all the lights out. The first room you go stright ahead and there will be a control room to you're right, press it and the cannon will be rdy to take off, but then you must go to the tallest part of the cannon and in the highest room, there will be a armless german who speaks english so just use the control room to take the cannon to the exsit and you will be revived into the real world. Hope that was the answer you wanted