Knowing that Al-Qaeda and Osama bin Laden were based in Afghanistan, President George W. Bush gave the Taliban an ultimatum: either hand over Osama bin Laden and his organisation, or the United States would strike with full force.
Congress passed legislation authorising the use of force in striking against terrorist targets.
Operation Enduring Freedom was the official name used by the Bush administration for the war in Afghanistan.
The aim of Operation Enduring Freedom was to find Osama bin Laden, remove the Taliban from power, and prevent the use of Afghanistan as a terrorist haven.
It began on 7 October 2001, when attacks were launched on Afghanistan by Western coalition forces along with the anti-Taliban Afghan Northern Alliance.
Special Force troops were sent in and by mid-November the Afghan capital of Kabul fell.
By mid-December, air attacks combined with ground forces toppled the Taliban regime.
Osama bin Laden was believed to have escaped to Pakistan during the battle of Tora Bora in December 2001.
Much of the Taliban had been destroyed or driven away by the end of 2001.
So, within two months, U.S. forces had removed the Taliban from operational power.
However, the war continued, as U.S. and coalition forces attempted to defeat a Taliban revolt based in neighbouring Pakistan.