The first ground attack came at the Battle of Umm Qasr on 21 March 2003, when a combined force of British, U.S. and Polish forces seized control of the port city of Umm Qasr. Baghdad, Iraq's capital city, fell to U.S. troops in April 2003 and Saddam Hussein's government quickly dissolved. On 1 May 2003, Bush announced that major combat operations in Iraq had ended. However, an insurgency arose against the U.S.-led coalition and the newly developing Iraqi military and post-Saddam government. The rebellion, which included al-Qaeda-affiliated groups, led to far more coalition casualties than the invasion. Other elements of the insurgency were led by fugitive members of President Hussein's Ba'ath regime, which included Iraqi nationalists and pan-Arabists. Many insurgency leaders were Islamists and claimed to be fighting a religious war to reestablish the Islamic Caliphate of centuries past. Saddam Hussein was captured by U.S. forces in December 2003 and was executed in 2006.