The end of the Iraq war in 2011 was a high point of President Obama's first term, marking the completion of one of his most important campaign promises. But as Islamic militants capture cities and towns throughout Iraq and march toward the capital, Baghdad, the president once again faces the criticism that his foreign policy has failed.
Worse yet, it stands to undermine his foreign policy legacy.
The violence has swept Iraq just two and a half years after the last U.S. troops departed following a nearly nine-year war. The gains made during the war have been wiped out with the rise of the Islamic State of Iraq and Syria (ISIS). The group's advance raises questions that will likely dog the president during the remainder of his time in office, from whether U.S. forces should have stayed behind, to how he might have tried to alter the course of events in recent years, to whether a similar policy in Afghanistan is doomed for failure.
Experts almost entirely agree that Mr. Obama could have done things differently, but differ on the question of how much blame he bears for the situation, when he might have changed course, and even whether it would have substantially changed the situation.
Why Iraq is plagued by violence
CBS News National Security Analyst Juan Zarate, a former Bush administration national security adviser, traces the trouble in part back to 2011, when U.S. troops withdrew from Iraq. Prime Minister Nouri al-Maliki refused to sign an agreement allowing for a residual force to remain behind, but Mr. Obama was also interested in bringing the war to an end, as he promised during the 2008 campaign.
That was a criticism from Sen. John McCain, R-Ariz., who faced off against Mr. Obama in the 2008 election on issues including Iraq policy.
"What the Americans left behind was an Iraqi state that was not able to stand on its own," he said Thursday.
Zarate argues that the lack of an American presence on the ground has limited the U.S. ability to support the Iraqi military and be prepared for an increase in violence.
"This is not America's fault, but we're certainly not in a good posture to deal with the situation and I don't think the administration has put us in a very good position to be able to respond with all options against this threat," he said.
But other experts argue that the U.S. had no choice but to respect Iraq's decision to end the American troop presence.
"Fundamentally the Iraqis asked us to leave and that was their prerogative and their choice," Brookings Institution senior fellow Michael O'Hanlon told CBS News.
Many people have pointed fingers at Maliki, who they say has weakened the Iraqi government and other institutions he controls, like the army. As the head of the Shiite-led government, he has become an increasingly authoritarian figure who has refused to take steps to integrate Iraq's Sunni and Kurdish minorities as the U.S. recommended.
"All the blame, in my view, rests with Maliki," said Michael Morell, the former deputy CIA director who now serves as a security analyst for CBS News. "He would not accept U.S. help, even behind the scenes, until recently, and he didn't keep the pressure on [ISIS]. You have to keep the pressure on the terrorist groups or they rebound quickly."
But Morell still says he's "not sure that had we left behind a small number of troops for training purposes, which is what it was going to be, that we would be a significantly different place now."
There are other theories about how Mr. Obama might have acted differently.
Center for Strategic and International Studies analyst Anthony Cordesman, a former Pentagon official, argued that the president, Vice President Biden, and the National Security Council have all been too quick to praise Maliki and give Iraq unconditional support in the years since U.S. troops left, even as it became clear there was a growing civil conflict.
He still sees room for the U.S. to influence Maliki's behavior in a way that could help stabilize the country as Iraq seeks U.S. aid.
"We do have the capability to put advisers in and to tie any of that aid to Maliki becoming something more realistic as a democratic leader, showing more respect for the rule of law and human rights," Cordesman told CBS News.
Yet a third theory on why Iraq has fallen into such chaos lies in the civil war in neighboring Syria, which has become a breeding ground for extremists groups like ISIS. The U.S. has refrained from active intervention in the Syrian conflict. Last August, Mr. Obama said he planned to seek congressional approval for a military intervention in the region but was forced to abandon the option and pursue diplomatic solutions amid low congressional interest.
The combination of what O'Hanlon called a "hands-off" approach in Syria and Maliki's increasingly sectarian leadership "has produced a witches' brew of terrorism, sectarianism, and insurgency within Iraq," O'Hanlon said.
Implications for Obama's foreign policy
Iraq is not the only foreign policy flash point to arise in recent months that has left Mr. Obama on the defensive. Critics have challenged his handling of Iran nuclear talks, Syria, Russian intervention in Ukraine, and the pending Afghanistan withdrawal. In a speech last month that sought to change the narrative about his actions, the president made the case that strong American leadership on the world stage doesn't mean it must be accompanied by military intervention.
"Just because we have the best hammer does not mean that every problem is a nail," he said in a speech last month to graduates of the United States Military Academy at West Point, defining his leadership style in contrast to the overzealous interventions of the Bush era.
A Washington Post editorial published Wednesday said the speech "triggered some interesting debate about the relative merits of engagement and restraint." But the newspaper called the results of the president's policies "increasingly worrisome."
"Total withdrawal can instead lead to challenges like that posed by Iraq today, where every option -- from staying aloof to more actively helping Iraqi forces -- carries risks. The administration needs to accept the reality of the mounting danger in the Middle East and craft a strategy that goes beyond the slogan of 'ending war responsibly,'" the editorial read.
Republicans are already calling for more aggressive action to stem the violence in Iraq, ranging from providing technical assistance and equipment to military intervention in the form of airstrikes. In the face of accusations from House Speaker John Boehner, R-Ohio, that he was "taking a nap" while extremists marched through western Iraq toward Baghdad, Mr. Obama pledged Thursday not to rule anything out as his team assesses the most effective way to assist the Iraqi government and prevent the jihadists from gaining a permanent foothold in Iraq or Syria.
But the breakdown in Iraq is already casting a shadow over the withdrawal from Afghanistan, which the administration hopes to claim as a victory. Mr. Obama has outlined the U.S. exit from Afghanistan in the last few weeks, announcing his intention to draw down forces after 2014 and remove all troops by 2016. Like Maliki, Afghan President Hamid Karzai has refused to sign the necessary agreement to allow forces to remain beyond the end of the year, but his successors have indicated they will.
The move still has both Republicans and foreign policy experts worried about a repeat of violence in Afghanistan.
"My fear is that Afghanistan in three or four years is going to mirror what's happening in Iraq today...with or without the number of troops we're talking about," Morell said.
Zarate, echoing several Republican lawmakers, said that the current breakdown in Iraq should serve as "a cautionary tale" for Afghanistan.
"The notion that we do not want any troops on the ground after two years regardless of the conditions, regardless of what the Afghans ask for, and regardless of the state of the Afghan military is to leave open the possibility that you'll see the fall of Kabul the way that we're seeing the potential fall of Baghdad," he warned.
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