A dismounted mechanized Infantryman takes out an Infantry Fighting Vehicle during a training exercise and is fixin to unass. Notice after the "kill" was assessed, the Commander of the vehicle "unbuttons" and is still trying to figure out where his killer is.

Different world, but the basic concepts are the same - vehicles can be extremely vunerable to infantryman due to restricted observation.
Formations help us react to surprises, and help knowing where everybody is at. This also helps killing other folks without killin' yourselves, (which is a good thing:)

Take a look at dismounted:
Fire Team Formations
Tactics, Techniques, and Procedures
Or, if you have a lot of time on your hands:
FM 7-8 Infantry Platoon and Squad
JOIN UP!
Battle of Andenne AAR
Task Force Ops 101
A modern Task Force slice on the move. Notice the tanks are covering their sectors. This provides security on the move so enemy can't sneak up on ya!
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