Read this: The first ground attack came at the Battle of Umm Qasr on 21 March 2003 when a combined force of British, American and Polish forces seized control of the port city of Umm Qasr. Baghdad, Iraq's capital city, fell to American forces 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 insurgency, 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 are Islamists and claim to be fighting a religious war to reestablish the Islamic Caliphate of centuries past. Iraq's former president, Saddam Hussein was captured by U.S. forces in December 2003. He was executed in 2006.

When was the first ground attack in the post-9/11 Iraq war?
What is the answer? (If it cannot be answered, return "unanswerable")
21 March 2003