Tactics - MCDP 1-3
Second, we want to draw our enemy unknowingly into a trap. This will often involve deceiving him. We make one course of action appear inviting. When he takes that course of action, we are waiting for him.
Third, an ambush is invisible. If the ambush is not invisible, it ceases to be an ambush and instead becomes a target for the enemy. Whether we are defending or attacking, the enemy must not detect us until it is too late for him to react. Surprise often depends upon invisibility. That invisibility may be provided through stealth in movement or in focusing the enemy's attention elsewhere to allow our forces to maneuver without detection.
The reverse slope defense is an example of using invisibility to spring an ambush. The enemy does not know we are there until he comes over the crest of a hill and is hit by our fires. His vehicles are hit on their soft underbellies. His troops are fully exposed to our weapons. Because he could not see us until the last moment, he could not call in artillery fire on our position. The reverse slope not only protects us from his direct fire; it protects us from his observation and thus his indirect fire. That is part of the ambush mentality: Do not let yourself be seen.
Fourth, in an ambush we want to shock the enemy. Instead of taking him under fire gradually with a few weapons at long range, we wait until he is within easy range of every weapon. We then open up suddenly, all at once, with everything we
