After defending the bridge, you’ll have to follow your squad to the forest where you’ll get a chance to jump on the unsuspecting mortar crew. Take them out until the remaining forces retreat further back. Before pursuing them, pick up this memento on top of one of the supply crates beside the second truck.
After surviving the artillery barrage and get separated from your team, walk past the dead pilot and head to the forest. After getting attacked by a patrol dog, check the plane wreck to the left and retrieve the memento from the pilot seat.
After reaching the bunker where the sniper is located, clear the lower floor and take the stairs. Before reaching the sniper’s hiding spot, turn around and jump on the ledge to find the memento on the seat.