The withdrawal of all US troops from Iraq was a complicated issue for both the Iraqi and US governments. The long, unpopular Iraq War drew sharp domestic criticism in the US — leading to legislative and legal efforts to force the end of the conflict. In Iraq, the new government was forced into a posture of defending Iraqi sovereignty from perceived American injustices, while simultaneously relying on US troops for support and security.

To legitimize the presence of coalition forces, the UN Security Council issued annual resolutions 1511 (2003) [PDF], 1546 (2004) [PDF], 1637 (2005) [PDF], 1723 (2006) [PDF], and 1790 (2007) [PDF]. The continuous renewal of these resolutions required both a request from the Iraqi government and the approval of the UN Security Council.

These renewals were predicated primarily on the argument that an early departure of coalition forces would lead to the collapse of the newly formed Iraqi government. In July 2007, the US began issuing Benchmark Assessment Reports to track the progress of Iraq towards stability. JURIST Guest Columnist Jide Nzelibe pointed out that public opinion of the war formed a major component of the debate over when the US should leave Iraq:

With respect to the termination of wars, the President and Congress have two strikingly different approaches to public opinion. Congress tends to react to public opinion when it constrains the President’s war initiatives … In contrast, the President tends to frame and shape public opinion in his role as the commander-in-chief. Rather than follow the course of public opinion when a war is going badly, the President is more likely to entrench himself into a war and gamble that the course of the war (and public opinion) will change in his favor.

So far President Bush has been able to convince Congress and the American public that it would be foolhardy to leave Iraq in its current stage. But he should be aware that the risk of civil war or anarchy is often not enough to assuage the American public to hold the course indefinitely, especially if American casualties continue to mount. President Reagan repeatedly warned the American public and Congress that Lebanon would descend into anarchy and possible occupation by Syria if American troops pulled out in early 1984, but Americans were simply fed up with the recurring scenes of American body-bags coming home from Beirut. President Reagan turned out to be right: the Lebanese civil war did get worse and the Syrians eventually started an occupation that lasts until the present day.

The last of the UN Security Council resolutions expired on December 31, 2008, following a final extension by the UN Security Council in December 2007. The potential absence of an international mandate for US troops led to protracted negotiations between the US and Iraqi governments. JURIST Guest Columnist Kevin Govern laid out the obstacles that the governments had to overcome in reaching an agreement allowing the coalition forces to remain:

One possible way to fill the legal “vacuum” after expiration would be a Status of Forces Agreement (SOFA), sometimes also referred to as a Status of Mission Agreement (SOMA) under UN Chapter VII auspices … The Council on Foreign Relations has noted that historically SOFAs have served as a “legal framework that defines how foreign militaries operate in a host country.” Typically SOFAs are established by executive agreement, rather than treaty, but are “without uniform or standard format for the document, which can vary in length and specificity.” … SOFAs may delineate, amongst other things, who is subject to criminal and/or civil jurisdiction of the host country to which they are deploying, as well as civil liabilities such as taxation.

The draft US-Iraqi SOFA proposal has been a point of negotiation since 2004, but pursued in earnest since March 2008, tentatively addressing immunity of American troops from Iraqi prosecution, the operations of over 60 military bases in Iraq, continued power to detain Iraqi prisoners, and protections for civilian contractors, (even though American contractors do not enjoy such immunity from local laws elsewhere).

Following December 2008, the presence of US forces in Iraq was governed by the US-Iraq Status of Forces Agreement (SOFA) [PDF], signed by Iraqi President Jalal Talabani. The SOFA was to be put to a referendum which never took place. It called for complete withdrawal of US troops by the end of 2011.

In February 2009, US President Barack Obama, speaking at a military base in North Carolina, announced that the US would withdraw all combat troops from Iraq by August 31, 2010:

What we will not do is let the pursuit of the perfect stand in the way of achievable goals. We cannot rid Iraq of all who oppose America or sympathize with our adversaries… We cannot sustain indefinitely a commitment that has put a strain on our military, and will cost the American people nearly a trillion dollars. America’s men and women in uniform have fought block by block, province by province, year after year, to give the Iraqis this chance to choose a better future. Now, we must ask the Iraqi people to seize it.

In the same speech, however, Obama declared that following withdrawal of combat troops, the US would maintain a force of between 35,000 and 50,000 troops to provide assistance to Iraqi security forces. The last “active” combat troops pulled out of Iraq on August 18, 2010, two weeks ahead of the self-imposed US deadline. Operation Iraqi Freedom officially concluded on August 31, 2010, when American involvement in Iraq was operationally renamed “Operation New Dawn,” pursuant to a February 2010 memo [PDF] from US Defense Secretary Robert Gates.

On October 21, 2011, nearly eight-and-a-half years after the war began, Obama announced that in keeping with the terms of the SOFA, the US would withdraw all forces from Iraq by the end of 2011. On December 15, 2011, a formal ceremony was held in Baghdad, officially ending the Iraq War. By December 18, 2011, all US troops and equipment were withdrawn from Iraq.