The War in Afghanistan was a conflict that took place from 2001 to 2021 in Afghanistan. It began when the United States and its allies invaded Afghanistan and toppled the Taliban-ruled Islamic Emirate. The war ended with the Taliban regaining power after a 19 years and 8 months-long insurgency against allied NATO and Afghan Armed Forces. It was the longest war in United States history, surpassing the Vietnam War by approximately five months.
Following the September 11 attacks in 2001, then-U.S. President George W. Bush demanded that the Taliban, then-de facto ruling Afghanistan, extradite Osama bin Laden, the mastermind of the attacks and who was, until then, freely operating within the country. The Taliban's refusal to do so led to the invasion of the country; the Taliban and their Al-Qaeda allies were mostly defeated and expelled from major population centers by US-led forces and the Northern Alliance. The Northern Alliance had been fighting the Taliban since 1996.