7 October 2001
The United States invasion of Afghanistan, codenamed Operation Enduring Freedom, took place after the destruction of the Twin Towers on 11 September 2001 in New York, United States of America, by the Al-Qaeda terrorist group. The event marked the beginning of the United States of America's "War on Terrorism". Afghanistan was invaded by the USA for failing to comply with a United Nations Resolution to hand over Osama Bin Laden, leader of Al-Qaeda ; an ultimatum to close terrorist training camps in Afghanistan, and "hand over every terrorist and every person and their support structure to appropriate authorities"; and give the US full access to terrorist training camps to verify their closure.
References
BBC,'2001: US launches air strikes against Taleban', From BBC,[Online],Available at: www.bbc.co.uk,[Accessed: 02 October 2013]