The invasion of Afghanistan was an attack launched by the United States and its allies, after the 9/11 attack. The main reasons why the United States invaded Afghanistan was that the U.S. recognized that the Al-Qaeda, the leader of a terrorist group had planned and caused the attacks of 9/11. Therefore, the principal objectives of this attack were to destroy Al-Qaeda and to refuse it a protected foundation of methods in Afghanistan. In this mission, the key ally of the U.S. was the United Kingdom.