2. Get on the train
O b j e c t i v e 1:
Your now in a ventilation shaft partially safe from all the germans below you. Move on and follow the path of the shaft. Upon falling out, exit the room but don't turn left at the corner. There are 10-13 nazis and all have a passion for killing Lt. Powell, whom willingly defied their master race. Use the peer-around-the-corner technique to take most out, using grenades to those that avoid. Clear out all the rooms and turn left at the end of the big hallway. There are a lot of nazis now in the level, and one of the big spawning points is down the stairs to your left. So hurry and clear the ones in front of you and go down the stairs. Safety...momentarily.
For now, take out a grenade and open the door in front (just one door!) and throw it in the vicinity of the guards to make them scatter. Exterminate all and continue (IGNORE THE BUNKER TO YOUR LEFT! Though its contains a canteen, once you get into it, there's little hope of coming out alive!) to the door ahead of you. There should be three or four guards coming out of it, depending on how much time you took to throw the grenade. Dispose of the rest and continue to a door with the sound of wind outside it.
O b j e c t i v e 2:
First, make sure your weapons are fully loaded. Then go through the door into the outside and KEEP MOVING. A train will pull up with cover fire off the endless enemies. Your goal is to get to the train within 120 seconds. Use the crates for cover, stopping frequently to dispose some of your troubles. Run into the train and get into it.