On September 18, 2001, President George W. Bush formalized the United States' military response to the recent September 11th terrorist attacks by signing the Authorization for Use of Military Force (AUMF) into law. This legislative act, passed overwhelmingly by Congress, established the legal framework and presidential authority for deploying U.S. armed forces against those responsible for the attacks. Its swift enactment underscored the national consensus and urgency following the unprecedented assault on American soil.

The AUMF specifically authorized the President to use "all necessary and appropriate force" against nations, organizations, or persons he determined "planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons." While its immediate focus was al-Qaeda and the Taliban regime in Afghanistan, which harbored al-Qaeda, the broad language allowed for a flexible and far-reaching application. This expansive mandate became the principal legal justification for military operations throughout the initial phase of what would become known as the global War on Terror.

The passage of the 2001 AUMF marked a significant moment in U.S. foreign policy and the balance of war powers between the executive and legislative branches. Unlike traditional declarations of war or time-limited authorizations, the 2001 AUMF did not include a sunset clause, meaning it remained active indefinitely unless repealed by Congress. This enduring legal authority has been subsequently invoked by multiple presidential administrations to justify military actions against various terrorist groups and associated forces in numerous countries, far beyond the initial scope of Afghanistan. The George W. Bush Presidential Library and Museum, Wikipedia, and the Council on Foreign Relations all present this event as a pivotal moment, focusing on its factual enactment and critical role in shaping subsequent U.S. national security policy, with no discernible disagreements on these core historical facts or framing.