Who lost Iraq? Sen. Graham blames Obama. The NY Times and even CNN ( to a lesser extent) agreed, in facts checks after a 2012 Obama-Romney debate, that Obama was scarcely energetic in negotiating a residual US troop presence.
The NY Times had a long, detailed account of the Status of Forces negotiations which made Obama's lack of commitment very clear. Time and memory permitting, I will find it [Michael Gordon, Sept 22 2012, "In U.S. Exit From Iraq, Failed Efforts and Challenges"].
And somewhere, Gen. Petraeus wrote an op-ed responded to written questions noting that Obama's critics are are engaging in speculation and that the prospective benefit of a US residual force was an untested hypothesis. But he seemed to be disappointed.
You oversaw the gains of the surge in 2007-08. How does it make you feel to see what is happening today, with ISIS having taken over more of Iraq than its predecessor, AQI [al-Qaeda in Iraq], ever did?
What has happened in Iraq is a tragedy — for the Iraqi people, for the region and for the entire world. It is tragic foremost because it didn't have to turn out this way. The hard-earned progress of the Surge was sustained for over three years. What transpired after that, starting in late 2011, came about as a result of mistakes and misjudgments whose consequences were predictable. And there is plenty of blame to go around for that.
What went wrong?
The proximate cause of Iraq’s unraveling was the increasing authoritarian, sectarian and corrupt conduct of the Iraqi government and its leader after the departure of the last U.S. combat forces in 2011. The actions of the Iraqi prime minister undid the major accomplishment of the Surge. [They] alienated the Iraqi Sunnis and once again created in the Sunni areas fertile fields for the planting of the seeds of extremism, essentially opening the door to the takeover of the Islamic State. Some may contend that all of this was inevitable. Iraq was bound to fail, they will argue, because of the inherently sectarian character of the Iraqi people. I don’t agree with that assessment.
The tragedy is that political leaders failed so badly at delivering what Iraqis clearly wanted — and for that, a great deal of responsibility lies with Prime Minister Maliki.
As for the U.S. role, could all of this have been averted if we had kept 10,000 troops here? I honestly don't know. I certainly wish we could have tested the proposition and kept a substantial force on the ground.
Where I think a broader comment is perhaps warranted has to do with the way we came to think about Iraq and, to a certain extent, the broader region over the last few years. There was certainly a sense in Washington that Iraq should be put in our rearview mirror, that whatever happened here was somewhat peripheral to our national security and that we could afford to redirect our attention to more important challenges. Much of this sentiment was very understandable given the enormous cost of our efforts in Iraq and the endless frustrations that our endeavor here encountered.
In retrospect, a similar attitude existed with respect to the civil war in Syria — again, a sense that developments in Syria constituted a horrible tragedy to be sure, but a tragedy at the outset, at least, that did not seem to pose a threat to our national security.
But in hindsight, few, I suspect, would contend that our approach was what it might — or should — have been. In fact, if there is one lesson that I hope we’ve learned from the past few years, it is that there is a linkage between the internal conditions of countries in the Middle East and our own vital security interests.
Well, Petraeus is being diplomatic in saying that "...the way we came to think about Iraq and, to a certain extent, the broader region over the last few years. There was certainly a sense in Washington that Iraq should be put in our rearview mirror...". Obviously, Obama and his progressive supporters felt that way. However, abandoning Iraq in order to prove that the war opponents were right all along was less of a priority for many Republicans.