Enemy Contact.  Open fire!  Defend the base.  Lock down the streets of the local town.  Hunt down the enemy in the forests.  Rescue the hostages from the caves.  Sweep the enemies out of the mountains. 

Fly in helicopters.  Ride in tanks and trucks.  Take it to the ground and get up close and personal with the enemy.  Your objective is simple:  Grab the biggest gun you can find, then knock out the enemy with your Heavy Fire!