War in Afghanistan (2001-2021)

The War in Afghanistan began in October 2001 when a United States-led coalition invaded the country to remove the Taliban government, which had harbored the al-Qaeda leadership responsible for the September 11 attacks that year. Coalition and allied Afghan forces toppled the Taliban government within weeks, but a NATO-led International Security Assistance Force mission that followed became bogged down in a long and costly counterinsurgency against a resurgent Taliban that lasted for the next two decades. The United States and the Taliban signed the Doha Agreement in February 2020, setting a timetable for the full withdrawal of foreign forces, and the final American and NATO withdrawal was completed in August 2021, accompanied by the rapid collapse of the Western-backed Afghan government and the Taliban's return to power in Kabul that same month. The war stands as the longest continuous armed conflict in United States military history and ended without the durable, internationally recognized non-Taliban Afghan state its intervention had originally sought to build.