Petraeus and Crocker both seem committed to a “blame Iran for problems” approach to their hearings. In this context, it’s worth looking at this in the broader context of US-Iranian relations. Iran is adjacent to Iraq. The United States has no diplomatic relations with Iran, and the U.S. government has branded Iran a member of the “axis of evil” and suggested that we are aiming to overthrow the Iranian government. Under the circumstances, it would obviously be hugely irresponsible of Iran to just let us consolidate an Iraqi regime that’s to our liking.
This is, simply put, a fight the Iranians can’t back down from. It’s the difference between us worrying about Iranian influence in Iraq (cause for concern) and us worrying about Iranian influence in Canada (panic!). The Iranians, in short, are never going to stop backing different Iraqi factions and trying to advance their interests there. Under the circumstances, there are basically three realistic options we could pursue. One would be to simply leave Iraq and acknowledge that, in practice, it’s difficult for any outside actor to manipulate Iraqi events precisely to the outside actor’s liking (just aask the United States). Another would be to attempt a rapprochement with Iran on a higher level, which would lay the groundwork for US-Iranian cooperation in Iraq. A third would be to combine the two.
But staying in Iraq in force while also maintaining a hostile relationship with Iran is just a recipe for frustration. As long as our big picture relationship with Iran is this bad, Iran is bound to some extent to be impeding whatever it is we’re trying to do in Iraq.