I was making the assumption that should the US chose to drop the atom bombs on those cities instead of just fire bombing them. I'm not sure how much more damage that would have done, or if those two were done together to try to prevent anything from growing there again, akin to what the Romans did to Carthage back in ancient times by destroying that city and covering it in salt to prevent anything from growing there again. (although that didn't happen because modern day Tunis exists there)