The Post-9/11 U.S. Counterterrorism Strategy refers to the comprehensive framework adopted by the United States following the September 11, 2001, terrorist attacks to prevent future attacks, dismantle terrorist networks, and combat global extremism, particularly Islamist groups like al-Qaeda. Its purpose was to enhance national security through a 'whole-of-government' approach integrating military, intelligence, law enforcement, diplomatic, and financial measures. Implementation included the passage of the USA PATRIOT Act for expanded surveillance powers, the Authorization for Use of Military Force (AUMF) enabling military operations, the invasion of Afghanistan in 2001 to oust the Taliban, the 2003 Iraq invasion justified partly on counterterrorism grounds, the creation of the Department of Homeland Security in 2002, enhanced CIA and NSA intelligence operations, global rendition and detention programs like Guantanamo Bay, drone strikes in multiple countries, and international coalitions such as NATO's involvement in Afghanistan. The strategy evolved over time, emphasizing preemption, with key documents like the 2002 National Security Strategy articulating the 'Bush Doctrine' of preventive war.