I'm all for putting Assad on trial, but that's a separate matter. The military campaign against Serbia that brought a halt to the war with Bosnia wasn't carried on until Milosevic was removed from office or surrendered for trial. The Serbs themselves took care of removing him from power, well after the end of fighting. Tony Blair still hasn't been put on trial. Nor has Netanyahu, and loads more. It's an imperfect worrld.

Insisting that Assad has to step down before there can be any attempt to make peace is just a way of making sure the war continues.