You know, it's possible that Harry didn't start the fight. It seems pretty likely to me, given the dogs' histories and the fact that Sophie was in heat, that Sophie could've started the fight, due to hormones and stuff, and Harry just came in once the fight had gotten started already. This happens a lot - one of the first things you should do when there's a dog fight is to get all the other dogs out of the area so they cannot join in.