Operation Enduring Freedom (OEF) was the official name used by the U.S. government for both the first stage (2001–2014) of the War in Afghanistan (2001–2021) and the larger-scale Global War on Terrorism. On 7 October 2001, in response to the September 11 attacks, President George W. Bush announced that airstrikes targeting Al-Qaeda and the Taliban had begun in Afghanistan. Beyond the military actions in Afghanistan, Operation Enduring Freedom was also affiliated with counterterrorism operations in other countries, such as OEF-Philippines and OEF-Trans Sahara.

The War in Afghanistan was an armed conflict from 2001 to 2021. It was the direct response to the September 11 attacks. It began when an international military coalition led by the United States launched an invasion of Afghanistan, declaring Operation Enduring Freedom as part of the earlier-declared war on terror; toppling the Taliban-ruled Islamic Emirate and establishing the Islamic Republic three years later. The Taliban and its allies were expelled from major population centers by the US-led forces, supporting the anti-Taliban Northern Alliance; however Bin Laden relocated to neighboring Pakistan. The conflict officially ended with the 2021 Taliban offensive, which overthrew the Islamic Republic, and re-established the Islamic Emirate. It was the longest war in the military history of the United States, surpassing the length of the Vietnam War (1955–1975) by approximately six months.