Iraq War: The United States, the United Kingdom, Australia, and Poland begin an invasion of Iraq.

The Iraq War, also referred to as the Second Gulf War, was a prolonged conflict in Iraq from 2003 to 2011. It began with the invasion by a United States-led coalition, which resulted in the overthrow of the Ba'athist government of Saddam Hussein. The conflict persisted as an insurgency that arose against coalition forces and the newly established Iraqi government. US forces were officially withdrawn in 2011. In 2014, the US became re-engaged in Iraq, leading a new coalition under Combined Joint Task Force – Operation Inherent Resolve, as the conflict evolved into the ongoing Islamic State insurgency.

The 2003 invasion of Iraq was the first stage of the Iraq War. The invasion began on 20 March 2003 and lasted just over one month, including 26 days of major combat operations, in which a United States-led combined force of troops from the United States, the United Kingdom, Australia and Poland invaded the Republic of Iraq. Twenty-two days after the first day of the invasion, the capital city of Baghdad was captured by coalition forces on 9 April after the six-day-long Battle of Baghdad. This early stage of the war formally ended on 1 May when U.S. President George W. Bush declared the "end of major combat operations" in his Mission Accomplished speech, after which the Coalition Provisional Authority (CPA) was established as the first of several successive transitional governments leading up to the first Iraqi parliamentary election in January 2005. U.S. military forces later remained in Iraq until the withdrawal in 2011.