Looters and vandals of a millennia old ruin full of nothing but destroyed lives? Acid rain will cause damage but I believe our concern should be stopping that, not worrying about what it will destroy..
Regarding soldiers, hopefully war never touches Italia again and the chance of Pompéi being bombed in a modern war is fairly low. We know where it is and the Geneva conventions list military actions on world heritage sites to be a war crime, no nation who recognizes that convention will intentionally target the ruins