This is for completing Act 2 Chapter 3 mission - AWOL. This is a story mission and cannot be missed. Gabe and Sid are BANNED from coming along on this mission, which leaves you with the Sniper Mikayla, and a troop of your choice off of your Roster.
Also, this mission is the introduction to Tickers in the game. Keep enough distance so that when it’s the enemy’s turn to move, they do not rush you and blow you to pieces.