Mission 1 | Collectibles Enemy Front Guide
Last update: 11 May 2016
The first collectible is next to the first fork in the sewers (right after you descend into the sewers).
The second collectible is inside the German building in the room full of cardboard boxes, on one of the shelves
The third collectible is in one of the rooms in the small building, on the yard in the second stage of the mission (after you exit the sewers, climb up the stairs, to the higher floor, or across the hole).