A war between a US-led coalition and Iraq that began with the coalition's invasion of the latter on 20 March 2003. US President George Bush and his administration justified the invasion with danger resulting from Iraq's alleged WMD program and support of Al-Qaeda, perpetrator of the 9/11 attacks 18 months beforehand, and with the need to promote democracy in the Middle East. Iraq's Baathist government quickly collapsed, and Baghdad was taken on 9 April. On 1 May, President Bush declared the end of major combat operations, and elections were held in 2005. However, the following years were characterized by insurgency campaigns led by both Baathist loyalists and other militant forces, which continued after the withdrawal of US combat troops, completed in 2011.