The Iraq War was a protracted armed conflict that began with the 2003 invasion of Iraq by a United States-led coalition, joined by the United Kingdom and several coalitions allies. The invasion regime toppled the government of Saddam Hussein. However, the conflict continued for much of the next decade as an insurgency emerged to oppose the occupying forces and the post-invasion Iraqi government. The United States officially withdrew from the country in 2011 but became re-involved in 2014 at the head of a new coalition; the insurgency and many dimensions of the civil armed conflict continue.
The invasion began on 20 March 2003, with the coalition allies launching a “shock and awe” bombing campaign. Iraqi forces were quickly overwhelmed as U.S. forces swept through the country. The invasion led to the collapse of the Ba’athist government; Saddam was captured on December 2003 in Operation Red Dawn and executed by a military court three years later. However, the power vacuum following Saddam’s demise and the mismanagement of the occupation led to widespread sectarian violence between Shias and Sunnis as well as a lengthy insurgency against U.S. and coalition forces. The United States responded with a troop surge in 2007 to attempt to reduce the violence. The U.S. began withdrawing its troops in the winter of 2007–08. The winding down of U.S. involvement in Iraq accelerated under President Barack Obama. The U.S. formally withdrew all combat troops from Iraq by December 2011.