There is no such thing as an atheist in a foxhole. A retreating enemy is probably just falling back and regrouping. The easy way is always mined. If you are short of everything but the enemy, you are in the combat zone. When you have secured the area, make sure the enemy knows it too.
Incoming fire has the right of way.
No combat ready unit has ever passed inspection. No inspection ready unit has ever passed combat. If the enemy is within range, so are you. The only thing more accurate than incoming enemy fire is incoming friendly fire. Things which must be shipped together as a set, aren't.