The U.S. invasion of Afghanistan begins with an air assault and covert operations on the ground, starting the longest war in American history.

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.