Take a leadership role with three sub-ordinates on Single Player, and expect to face most of the attacks.
Lastly, if you’re light on actual human friends, you can play through all five campaigns with three computer-controlled chums in Single-Player mode.
When you’ve chosen the campaign and stage you want, the game continues until you reach the Finale at the end of that campaign. Take the lead role, as the A.I. teammates follow your lead.
This means some cross fire and enhanced strategic stances aren’t possible, and you alone are responsible for how quickly you move through the stages.
Don’t move too far ahead of your teammates, though, as dying results in a restart. If others die (after three possible rescues), they move to a Rescue Closet and are released when you open the door.