The Subway Tunnel (2)

The game mentions that you cannot achieve the Rescue Ranger, Invisible Man, and Hedge-hopper achievements in a single playthrough as they are incompatible.

To get the Hedge-hopper achievement, you must kill all enemies, including the Red prisoners. Key kills include: the two Reds behind the troop transport, letting the guy under the tracks be executed (do not kill the interrogators beforehand), the two wounded Reds behind the Red frontline, letting the Fascist execute a prisoner or using a hand grenade in the cell (incendiary and sticky grenades may not always work), and the two Fascists in the railcar.

To get the Invisible Soldier achievement, you cannot kill anyone, but you can knock enemies out.

To get the Rescue Ranger achievement, knock out the Fascist before he executes the Red prisoners. It is now possible to achieve Invisible Soldier and Rescue Ranger in the same game.

To gain a Moral Point, listen to the entire conversation of the Red leader near the troop transport train.

If you need help reaching the manhole, refer to [4.1.1 Frontline - Invisible Man].

The quickest way to get through Communist and Nazi lines is to sneak down the stairs to the left of the railcar, past the two guards on the lower platform, blow out the lamp, and wait for the guards to ascend the stairs before proceeding behind Nazi lines.

The railcar can be destroyed by luring it to the top of the stairs and using a grenade. It remains stationary in front of the doorway but moves elsewhere on the tracks. Be aware that the railcar can run you over.

To prevent the enemy from killing the middle prisoner (the Red leader), either kill the guard or alert him. You must kill the two guards on the tracks and the four enemies below. The middle prisoner stands up when he can be rescued; approach him for an achievement and a Moral Point. Kill the enemy at the far end of the tunnel by the exit door.