United States invasion of Afghanistan

Shortly after the September 11 attacks in 2001, the United States declared the war on terror and subsequently led a multinational military operation against Taliban-ruled Afghanistan. The stated goal was to dismantle al-Qaeda, which had executed the attacks under the leadership of Osama bin Laden, and to deny al-Qaeda militants a safe base of operations in Afghanistan by toppling the ruling Taliban government. The United Kingdom was a key ally of the United States, offering support for military action from the start of the invasion preparations. The American military presence in Afghanistan greatly bolstered the Northern Alliance, which had been locked in a losing fight with the Taliban during the Third Afghan Civil War since 1996. Prior to the beginning of the United States' war effort, the Taliban had seized around 85% of Afghanistan's territory as well as the capital city of Kabul, effectively confining the Northern Alliance to Badakhshan province and smaller surrounding areas. The American-led invasion on 7 October 2001, marked the first phase of what would become the 20-year-long war in Afghanistan.

After the September 11 attacks, American president George W. Bush demanded that the Taliban government hand over Osama bin Laden to the United States, and also expel al-Qaeda militants from Afghanistan; bin Laden had been active in Afghanistan since the Soviet–Afghan War and was already wanted by the Federal Bureau of Investigation for his role in the 1998 United States embassy bombings. The Taliban refused to extradite bin Laden unless the US produced evidence of his guilt. The Taliban did not respond to the demands to shut down terrorist bases or extradite other suspected terrorists. In response, the United States launched Operation Enduring Freedom on 7 October 2001, alongside the United Kingdom. The two countries were later joined by a large multinational force, made up of multiple NATO members and two of their major non-NATO allies, as well as Afghanistan's local Northern Alliance. The invasion effort made rapid progress for the next two months as the coalition captured Kabul on 13 November and toppled the Taliban by 17 December, after which international military bases were set up near major cities across the country. However, most members of al-Qaeda and the Taliban were not captured: during the Battle of Tora Bora, several fighters including bin Laden, the founder of al-Qaeda escaped into neighboring Pakistan or otherwise retreated to remote regions deep within the Hindu Kush.

In December 2001, the United Nations Security Council established the International Security Assistance Force (ISAF) to oversee military operations in Afghanistan and also train the new Afghan National Security Forces. At the Bonn Conference that same month, Hamid Karzai was selected to lead the Afghan Interim Administration. Simultaneously, the Taliban's founding leader Muhammad Umar reorganized the movement to wage asymmetric warfare against the coalition, and by 2002, the group had launched an insurgency against the American-led war effort. Protracted fighting continued for the next two decades, and by mid-2021, the international coalition and the United States had begun to withdraw from the country amidst a nationwide Taliban offensive. In August 2021, the Taliban captured Kabul and toppled the Afghan government, re-establishing their rule in the form of a second Islamic emirate.