Yeah, they were mortal enemies before the war. You could tell by the way that Islamists were immediately captured and killed when they came into Iraq. Oh, wait. They were sheltered and protected, weren't they? And by the number of bombings of Saddam's facilities by the Islamists. Oh, wait. There weren't any. For some mysterious reason the Islamists were only killing Kurds. Have you been paying any attention at all to what I've been saying?

If they are working together now, there is not one reason they could not have been working together three years ago. It's not like we were any less hated by either group back then.