Follow the path and you'll see the Declassify Mission skull. If you choose to activate it, extra locust forces will attack from behind. Continue further along the barricaded road and kill the mortar-wielding locust. Kill the enemy reinforcements and grab the mortar yourself. If you have the declassify mission active, beware of the enemy locusts that will appear from the rear.
You'll eventually reach a closed checkpoint gate ahead. A couple of beastriders will burst through so kill them and proceed forth. You'll find a COG tag skull ahead. To its right lies a blue container van. The COG tag is located beside that container van's side.
J. Carlson, CPT, Halvo Bay
Kill all the remaining enemies in the area and then regroup with your team at the exit to complete the section.