>use troops to hold a zone in buildings
>they get deleted with mass artillery and bomb salvod from out of nowhere and theres nothing you can realistically do to stop it

I think there needs to be a 'run to underground shelter' command to minimize troop losses for those situations.
You would still incur losses and lose the ability to shoot at enemies to retain favor to the attacker, but not just wipe out your men for free with one salvo. If it was that easy irl city assaults would have been 2 week operations.