Make it too tough for the enemy to get in and you can't get out. Tracers work both ways. The only thing more accurate then incoming enemy fire is incoming friendly fire. Radios will fail as soon as you need something desperately. When both sides are convinced that they are about to lose they are both right.
Professionals are predictable, but the world is full of amateurs.
All weather close support doesn't work in bad weather. The bursting radius of a grenade is always one foot greater that you're jumping range. The only terrain that is truly controlled is the terrain on which you stand. The law of the bayonet says that the man with the bullet wins. Cluster bombing from B52's and C-130's is very accurate the bombs always hit the ground.