Saddam's government did not respond to the ultimatum in the way that the Bush Administration wanted them to, and therefore, on March 19, 2003, the Coalition Forces of the United Kingdom and United States, with Australian, and Polish assistance began to invade Iraq. In the process, Saddam's military was defeated and dispersed. In the south, V Corps (United States), I Marine Expeditionary Force, and numerous divisions of the British Army, defeated the Iraqi 3rd Corps, the Republican Guard, and much of the Fedayeen Saddam. In the north, Task Force Viking, a special operations led task force, defeated the Iraqi 1st and 5th Corps and attached other Republican Guard elements. Significant battles included the Battle of Nasiriyah and the Battle of Baghdad. The British Army controlled the southern regions of Iraq and maintained a peace-keeping presence in the country until their withdrawal on 30 April 2009. The United States controlled Northern and Central Iraq. After the invasion, the Coalition Provisional Authority was established to administer the Post-invasion Iraq, 2003–present.