American and British forces began air strikes in Afghanistan on October 7, 2001, almost four weeks after the attacks on New York and Washington. The targets were air defence sites, airfields and Taliban positions around Kabul, Kandahar and Jalalabad. Bush had demanded that the Taliban government hand over Osama bin Laden and shut down the camps of al-Qaeda, and the Taliban had refused. Within weeks, small teams of American special forces were on the ground with the Northern Alliance, calling in strikes.
Support was assembled quickly. The United Nations Security Council passed resolutions 1368 and 1373 in the days after September 11, NATO invoked Article 5 for the first time in its history, and Pakistan, which had been the Taliban's closest backer, agreed to open its airspace and to break off diplomatic relations. The Northern Alliance, made up of Tajik, Uzbek and Hazara militias that had spent years fighting the Taliban out of the Panjshir valley north of Kabul, supplied the infantry the campaign needed and took the cities once air power had broken the front lines.
The collapse was fast. Kabul fell on November 13, Kunduz two weeks later, and Kandahar, the movement's home city, surrendered on December 7. A conference at Bonn in December installed Hamid Karzai as head of an interim administration, and a United Nations mandated force was deployed to Kabul. Bin Laden was not caught. He left through the mountains at Tora Bora in December and was found in Pakistan ten years later.
What followed ran for twenty years, the longest war in American history. The Taliban regrouped inside Afghanistan and across the border from 2003 onward, the international force grew to more than 130,000 troops at its peak, and withdrawal dates were repeatedly moved back. The last American aircraft left Kabul on August 30, 2021. The Taliban took the country within days, and the government installed at Bonn in 2001 fell almost as soon as the foreign troops were gone.