You don't kill a city.

"16 But of the cities of these people, which the LORD thy God doth give thee for an inheritance, thou shalt save alive nothing that breatheth: 17 But thou shalt utterly destroy them; namely, the Hittites, and the Amorites, the Canaanites, and the Perizzites, the Hivites, and the Jebusites; as the LORD thy God hath commanded thee: 18 That they teach you not to do after all their abominations, which they have done unto their gods; so should ye sin against the LORD your God."

They sacrificed and ate children. Remind you of anyone? Only difference today is the Jews have brought in raping the kids beforehand.