Battle of Nasiriyah, first major conflict during the invasion of Iraq.

The Battle of Nasiriyah was fought between the US 2nd Marine Expeditionary Brigade and Iraqi forces from 23 March to 2 April 2003 during the US-led invasion of Iraq. On the night of 24–25 March, the bulk of the Marines of Regimental Combat Team 1 passed through the city over the bridges and attacked north towards Baghdad. However, fighting continued in the city until 1 April when Iraqi resistance in the city was defeated. Relative to other battles in which very few coalition forces were killed, the Iraqi defenders in Nasiriya inflicted relatively heavy casualties on coalition forces and put up more stiff resistance.

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.