> investigate after they left

We tried this terrible idea once. It results in our guys dying because surprise, they detonate the ied when you walk up to it.

> shoot the legs not the heads

Have you ever watched programmers on tv doing things like 3 people typing on the same keyboard? That's the equivalent of this statement.

> Don't shoot unless shot upon

They fight by planting ieds. In your world, we'd be dying by the dozens. Interdicting the guys planting IEDs is the most effective way to prevent IED attacks.