Oh it'll come, just don't think about it and play the game. I was on Nelson Bay attacking the first A. I shot a grenade launcher at one of the walls while someone was hitting it with mortar strike. It turns out I got all those demolition kills and it was 5. Those were the only demolition kills I had so far in this game. I don't really try to destroy the buildings. If it's standing on its last leg, I'll just take out the entire building.