Battles & Wars › Modern conflicts
War on Terror
2001 onward· War· Middle East & Africa
Well documentedSolid records, physical evidence or scientific consensus.
The US-led global campaign against al-Qaeda and other militant groups launched after the September 11, 2001 attacks.
See it on the Battles & Wars map →What happened
President George W. Bush declared a 'war on terror' days after 9/11. It included the invasion of Afghanistan in 2001 and, more controversially, of Iraq in 2003, plus drone strikes and special-forces raids in Pakistan, Yemen, Somalia and elsewhere. At home it brought new surveillance powers under the USA PATRIOT Act, the Department of Homeland Security, and detention at Guantánamo Bay. Osama bin Laden was killed in Pakistan in 2011; ISIS rose and lost its territory by 2019.
Why it matters
It reshaped US foreign and security policy for two decades, cost trillions of dollars and hundreds of thousands of lives, and sparked lasting debates over torture, surveillance and civil liberties.
How we know
The 9/11 Commission Report, the US Senate's 2014 report on CIA interrogation, cost and casualty estimates by Brown University's Costs of War project, and government and press records.
Still debated
Whether it reduced or increased terrorism overall is debated, and it has no clear end; the US never formally declared it over.
Inside this (5)
Connections (5)
▸September 11 attacks launched War on TerrorWell documented
The connection
Nine days after the attacks, President Bush told Congress the war on terror would not end until every terrorist group of global reach was defeated. Congress had already passed an Authorization for Use of Military Force (AUMF), still used two decades later to justify strikes on al-Qaeda and related groups.
When and how
Washington, September 14–20, 2001: Congress passed the AUMF on September 14, and Bush addressed Congress on September 20.
How we know
The text of the AUMF and Bush's speech are public; later administrations' legal opinions cite the AUMF.
Debates and open questions
Whether a 'war' framing was right, rather than treating terrorism mainly as crime, and how far the AUMF stretches, are still debated.
▸War on Terror was invoked to justify Iraq WarWell documented
The connection
After 9/11 the Bush administration argued that Saddam Hussein might hand weapons of mass destruction to terrorists, and claimed links to al-Qaeda. Framing Iraq as part of the war on terror helped win public and congressional support in 2002. Investigations later found no operational ties and no active weapons stockpiles.
When and how
Washington, 2002–03: Bush's 'axis of evil' speech (January 2002), Congress's October 2002 war authorization, and Colin Powell's UN presentation in February 2003.
How we know
The 9/11 Commission found no evidence of a collaborative operational relationship between Iraq and al-Qaeda; the Duelfer Report and Senate Intelligence Committee reviews (2004, 2008) found the WMD case was wrong.
Debates and open questions
Whether officials sincerely believed the threat or stretched thin intelligence remains debated; many historians argue 9/11 lowered the risk Washington would tolerate.
▸War on Terror relied heavily on Drones and precision strikeWell documented
The connection
Hunting small, scattered militant groups in countries where the US was not formally at war suited drones, which could watch a target for hours and strike without risking pilots. Strikes spread to Pakistan, Yemen and Somalia; President Obama authorized about ten times as many as President Bush, and they continued under later presidents.
When and how
The first strike outside a war zone killed an al-Qaeda leader in Yemen in November 2002; strikes in Pakistan's tribal areas peaked in 2010.
How we know
US government disclosures from 2016, leaked documents, and independent tallies by the Bureau of Investigative Journalism, New America and Airwars, which differ on civilian deaths.
Debates and open questions
Whether drone strikes weakened terrorist groups or created new recruits through civilian deaths, and whether they are legal outside declared wars, remain debated.
▸US strikes on alleged drug boats (Operation Southern Spear) borrowed the legal logic of War on TerrorDebated
The connection
After 9/11 the US treated al-Qaeda members as combatants who could be killed anywhere, not suspects to arrest. In 2025 the administration applied similar logic to cartels: it designated them terrorist organizations, told Congress the US was in an 'armed conflict' with them, and called boat crews unlawful combatants.
When and how
Cartel terrorist designations in February 2025, strikes from September 2025, and the armed-conflict notice to Congress in October 2025.
How sure are we?
The designations and notices are public, and terms like 'narco-terrorists' echo War on Terror language; how closely the legal theories match is debated.
Debates and open questions
Legal scholars dispute whether drug trafficking can be an armed attack and whether any law passed by Congress covers cartels; the administration relies on presidential power.
▸Military-industrial complex (Eisenhower's 1961 warning) expanded with private contractors during the War on TerrorWell documented
The connection
After 2001 the Pentagon relied heavily on private companies for food, fuel, bases, security and intelligence. In Iraq and Afghanistan, contractors at times outnumbered US troops. Firms such as KBR, then part of Halliburton, won multibillion-dollar contracts, and private security companies such as Blackwater guarded officials.
When and how
Iraq and Afghanistan, 2001–2021; Blackwater guards killed 17 Iraqi civilians at Nisour Square, Baghdad, in September 2007.
How we know
Congressional Research Service contractor counts, the 2011 Commission on Wartime Contracting report and US court cases document the expansion.
Debates and open questions
The 2011 commission estimated $31–60 billion lost to waste and fraud; whether outsourcing saved money overall is still debated.