The War Machine missions require that you destroy the four War Machines, marked by an "L" on the map. There are two missions for each War Machine; one for killing the Overseer for the map to the machine, and another for destroying the machine. Get 100% Synch by performing the corresponding tasks in the following missions:
"Flying Machine 2.0" mission
Do not get shot while using the Bomber. Reward is Bomber model.
"Hell On Wheels" mission
Do not take damage while using the tank. Reward is Tank model.
"Loose Cannon" mission
Open 1 of the first 3 gates, Reward is Naval Cannon model.
Do not kill anybody before destroying the blueprints. Reward is Machine Gun model.