1. The Great Escape

Locust Shell Disposal Form

You begin Act 4 by walking. You'll hop down and jump over a barrier. Take a left after you do, and you'll find the collectible behind a crate on your left.

2. No Detours

COG Tag (K. Rush)

You begin the second chapter of act four in much the same way that you begin, well, pretty much every chapter: walking. You'll hop down off a ledge, and on your left side, you'll see a gigantic gear. Approach it and look for the corpse of a fallen soldier. On the body, you'll find COG tags for K. Rush / PVT / Bronn 21525112.

3. Knock Knock

COG Orders

After climbing a few ladders, you'll enter a courtyard for a particularly difficult fight. Clear the area first.

Walk into the first doorway on your left, relative to where you entered the courtyard. Turn right, and in the far left corner of that room (up a few stairs), you'll find this chapter's lone collectible.

4. Powerless

COG tag (P. Wood)

On your way to the top of the building, the elevator will break down. You'll get out, make your way through a couple of gigantic gears and have a bit of a fight. Then it's time to open another door that requires two people pressing big, red buttons simultaneously.

Open the door, walk into the hallway, take your first left, and walk to the far side of the island in the middle of the room. There, you'll find the COG tags for P. Wood / CPL / Halvo Bay 20256192.

Rations Schedule for Abandoned Gears

Continue through the rooms on your way to your destination. You'll need to open a red double door to get into the next area. Then you'll have a fight among enormous chains that change the cover on the battlefield.

When your enemies are dead, make your way through the door on the far side of the room. Turn left in a room where you see 13E written on the wall, and hang a right at the corner. The collectible is sitting on wooden crates against the right wall.

5. Storm Warning

COG Tag (E. Yates)

As soon as you enter the substation, look for a door on the right wall. Go through, turn left, and sitting on the desk you'll find COG tags for E. Yates / CPL / Landown 08821139.

Letter

Start in the room where you vented and shot the coils to clear your way. (Good idea, dad!)

Grid View

Walk straight ahead, up two small flights of stairs and take a left at the intersection. Walk through the first door on the left and keep going and follow the hallway around until you see a room whose door is half-filled with sandbags. Hop over the sandbags, and you'll find the collectible in that room next to, yeah, another corpse.