[Mobhack]

If you want them to go boom, put a booby trap (explosives) there.

Defenders will wander off if an objective is in enemy hands - are the objectives shared at the start of the game?. If the attacker "owns" even one, the defenders will step off to take that as their reaction turn is reached or sometimes if its nearby and/or very high value IIRC.

Also applies if "neutral" ones have been placed over defenders ones to big up the points of a few scattered objective areas - same result as neutral is not "mine" in the defender's eyes..

(I'll assume the defenders do have reaction turns set, other than say 0 or default which is usually the same effect as 0 turns)