I argued for 25,000 US troops. I even speculated about how to make a virtually symbolic presence of 10,000 work. But no, we left. And Iraq fears Iran too much to resist Iranian pressure over the Syria issue and is too corrupt to prevent al Qaeda from regenerating.
I wanted the troops for deterring Iranian attacks, of course. But that was relatively minor. I mostly wanted our troops there for training, for help in counter-terror operations; and mostly I wanted our troops there for domestic Iraqi tranquility. With US troops there, all factions would know that resorting to violence to settle disputes would not work. We'd always be the strongest faction, military-wise. And most important, as I argued, our troop presence would be a force that would keep Iraq settled enough to focus on rule of law in Iraq. We could use civilian advisors to hunt corruption in the government, courts, and police and military agencies. Do all those things, and Operation Iraqi Freedom would result in freedom and prosperity for Iraqis after decades of war and Saddam's depravity.
And while I could not have predicted this back then, our presence would likely have kept Assad from having his ground and aerial lifeline through Iraq to Iran.
We haven't been in Iraq, of course, for nearly two years. Violence is up--although not anywhere near peak levels of sectarian slaughter--and much of this violence is because of the corruption (lack of rule of law):
While the U.S. was still in Iraq (up to 2011) American and Iraqi counter-terrorism efforts managed to tear up the Islamic terrorist groups. Many Sunni Arab terrorists accepted (with some trepidation) various amnesty deals. Al Qaeda, which is still largely a foreign outfit, was crippled with the killing or capture of most of their senior leaders. Being foreigners, and favoring attacks on civilians, made al Qaeda the most hated group in the country. There were plenty of tips from concerned citizens because of that. Iraqi members of al Qaeda often switched to criminal gangs, relegating Islamic terrorism to the "what I do in my spare time" category. While the U.S. contributed lots of essential (UAVs, intelligence collection and analysis) support for the counter-terror battle, the Iraqis did most of the work on the ground. The Iraqi cops took advantage of the fact that most Iraqis want peace. Three decades of Saddam's misrule, and nine years of post-Saddam terror have created a widespread desire for less unrest. While there are far fewer terror attacks (less than ten percent of those five years ago), they persist, and police believe there are enough diehard Islamic radicals and violent criminals to keep the bombs exploding for another five years or more.
But after the Americans left the Iraqi police lost the services of the American intelligence and special operations troops. The Americans were much better at collecting, analyzing and acting on information. The American special operations troops inspired their Iraqi counterparts to high levels of performance. But the Americans also kept the corruption in the police in check. U.S. intelligence also monitored the Iraqi police and it was difficult for Iraqi cops to be dirty without that traitorous activity being made public by the Americans, or acted on by Iraqi officials after pressure from American diplomats. With the Americans gone the police corruption quickly escalated to the point where the terrorists could get any information or assistance they wanted if they were willing to pay enough bribes or intimidate the right cops (kidnapping family members often worked). The subsequent rise in terrorist violence has created growing public anger and politicians are now considering what was previously unthinkable; actually doing something about the police corruption. They may have to, because the Americans have been lukewarm to the idea of sending back some of their intelligence and special operations troops.
I'd send our intelligence and special operations people back--and encourage our allies to return special forces back to Iraq, too. If Iraqi agrees, of course.
The bright side is that the Iraqi politicians seem to be reacting to public anger by thinking they need to perform better to get votes rather than figuring out how to bypass elections to restore (a kinder and gentler) autocracy.