Is Iran the biggest problem in Iraq?

Over a meal this weekend at a Green Zone chow hall (chicken salad and Baskin-Robbins pralines and cream ice cream, a KBR delight), I had a revealing conversation with two senior U.S. military officials.

"We've pretty much defeated al-Qaida here," one of the military officers said. "If Iran stopped doing what it's doing, things would dramatically change."

"You think that would be it, a turning point? If Iran stopped backing militias, you think things would get much better?" I asked.

"No doubt. It would be dramatic," replied the officer.

For many military commanders there is a feeling of euphoria that the U.S. troop "surge" and the top commander in Iraq Gen. David Petraeus managed to reduce violence, especially in Sunni areas.

The surge has become something sacred for the military in Iraq. It was a plan that worked. It has been entered into the annals of history – at least here – as a success, not to be questioned. The commanders I spoke to this weekend were angry Iran, they claim, is trying to ruin their surge.

The frustration is understandable. Sunni radicals have gone quiet, thanks in part to the "Sons of Iraq" program in which former insurgents (mostly Sunnis) are paid to fight al-Qaida. (Critics say the program is just arming the insurgents to fight another day).

Anbar province, once considered a lost region overrun by Sunni radicals, is now mostly calm. It is the Shiite areas, especially where Iran is strong, like in Basra and Sadr City, which are now in revolt.

U.S. military commanders deduce that if Iran stopped stoking the fires of conflict, both Sunnis and Shiites would stop fighting long enough for Iraq to blossom into the prosperous nation that U.S. officials promised and that the U.S. military needs to prevent failure in Iraq.

Perhaps they are correct. It would be logical to assume that if both sides stop fighting, there would be less bloodshed and more room for dialogue.

The problem, however, is that Iran is only the U.S. military's latest enemy in Iraq. It is only the latest spoiler here. There have been others, each considered vital at the time; yet the war continues.

U.S. Enemies:

2003: Saddam Hussein and his alleged weapons of mass destruction and supposed alliance to al-Qaida.

2004-2005: Sunni insurgents, former Baath party members and Syria, all of whom allegedly wanted to stop democracy and freedom.

2006-2007: Sectarian gangs, and Abu Musab al-Zarqawi's "al-Qaeda in Iraq."

2008: Iran's "Special Groups," militias backed by Iran's Revolutionary Guards

Is this the end? Is Iran, as U.S. military officials suggest, the lynchpin to success in Iraq? Or is it just the flavor of the month?