How NATO responded to 9/11

NATO has only invoked its mutual defense clause once, in the days after the 9/11 attacks.

NATO's Article 5 has been invoked once—after 9/11

The article was invoked the day after the attacks and launched a series of NATO campaigns to fight global terrorism. This page includes excerpts from a speech by then-NATO Secretary General Jens Stoltenberg about the attacks and the organization’s response.

The treaty's Article 5 requires mutual defense, but not necessarily military action.

Members decide to what extent they respond to an attack on an ally

The NATO constitution is intentionally vague about what exactly is required from its members. Explore the historical debates and learn more about common misconceptions about NATO’s common defense clause.

NATO was formed in 1949 to deter Soviet expansion, prevent European militarism, and encourage political integration.

9/11 reshaped US foreign and military policy for decades, shifting focus to non-state actors and the Middle East.

The alliance operates under a "flexible response" doctrine—that is, proportionality

NATO countries' main deterrent against aggression is their ability to respond with nuclear weapons. This video from "The Infographics Show" outlines the purpose of this nuclear arsenal, NATO’s strategy to prevent attacks, and its plans in the event of escalation toward nuclear war.

Watch the historic treaty signing that established NATO in 1949

NATO was created with the signing of the North Atlantic Treaty on April 4, 1949, in Washington, DC. The clip embedded in the webpage includes a newsreel with an excerpt from US President Harry Truman’s speech celebrating the historic day.

The US launched the Global War on Terror after 9/11

In the wake of 9/11, the US declared a Global War on Terror—initiating military operations in Afghanistan and Iraq, expanding surveillance, and forming international coalitions to combat terrorism and disrupt extremist networks worldwide.

Experience 9/11, the deadliest terrorist attack on American soil, as it happened.

The 2001 Authorization for Use of Military Force has been used by five administrations to justify military operations in at least 22 countries.

NATO consists of 32 countries across North America and Europe.

President Bush addressed the nation on 9/11 from the Oval Office, watched by an estimated 80 million people.

NATO condemned Russia's 2022 invasion of Ukraine

While Ukraine is not a member, NATO responded forcefully to the Russian invasion of the country in 2022. This page from the NATO website offers answers to frequently asked questions about NATO’s response to the invasion, specifically on how NATO is aiding Ukraine.

Americans showed an unprecedented surge of patriotism after 9/11

In the weeks following 9/11, 79% of US adults reported displaying the American flag, and a year later, 62% said they "often felt patriotic" due to the attacks.

9/11 was the first global disaster watched in real time across the world

As the first plane struck at 8:46 a.m. ET, CNN's live feed broadcast images worldwide within minutes. An estimated 2 billion people watched the collapse of the Twin Towers live.

Decisions at NATO are by consensus and must be unanimous

There are two strategic commands in NATO: one in Europe (Supreme Allied Headquarters Command Europe) and another in Norfolk, Virginia (Allied Command Transformation). The alliance is headed by both a military officer and a civilian leader.

One Day in America series reveals the full timeline and human toll of 9/11

This National Geographic episode reconstructs the events of 9/11—highlighting the Pentagon attack, Flight 93 hijacking, South Tower collapse, and rescue efforts—offering a detailed, chronological account of how the day unfolded.

Osama bin Laden declared jihad—a call for armed struggle framed as a religious duty—against the US in 1996.

9/11 permanently changed air travel security in the US with the creation of the Transportation Security Administration.

The PATRIOT Act expanded government surveillance after 9/11

Signed into law weeks after the attacks, the PATRIOT Act granted federal agencies sweeping powers to monitor communications, access records, and conduct surveillance—sparking ongoing debates over privacy, civil liberties, and national security.

View artifacts at the Smithsonian that tell the story of 9/11.

The US and allies invaded Iraq based on flawed intelligence about potential weapons of mass destruction.

Vladimir Putin was the first world leader to call Bush after 9/11, and visited the US two months later.

The attacks prompted a quick jump in American public support for war

In a Gallup poll taken days after the attack, an extraordinary 97% of Americans approved Congress declaring war on Japan—reflecting overwhelming national unity in the wake of the strike.

After the 9/11 terrorist attacks, The Onion stuck with satire, defying what some were predicting was 'the death of irony.'

US intelligence warned in multiple reports of al-Qaida's plans to strike before 9/11.

As of 2025, every NATO member spent at least 2% of GDP on defense, a target the alliance had been pushing toward for over a decade.

Coverage of the 9/11 terrorist attacks helped shape Wikipedia's editorial policies

Launched nine months earlier, the site was featured on Yahoo's news page, attracting traffic from information seekers as dozens of new editors created hundreds of articles, including memorials, conspiracy theories, and donation and volunteer pages. Discussions between editors would begin establishing rules for handling breaking news events.

President Bush threw the first pitch at the World Series in New York City less than two months after 9/11.

Tensions between the US and European NATO allies

The Associated Press article discusses US Defense Secretary Pete Hegseth's assertion in February of 2025 that restoring Ukraine's prewar borders or NATO membership for the country are both unrealistic. This represented a large rift between the United States and its other NATO allies, prompting concern about America’s commitment to the future of the alliance.

Welcome to Gander, a tiny town of around 10,000 people in Newfoundland, which took in nearly 7,000 passengers for days after the 9/11 attacks grounded all air travel in the US.

One hijacked plane struck the Pentagon on 9/11, killing 125 people inside

American Airlines Flight 77 crashed into the Pentagon's west side, destroying a section of the building and killing all 59 on board, along with 125 military and civilian personnel, making it the deadliest attack on the US military headquarters.

al-Qaida targeted multiple US interests in attacks before 9/11

Before 9/11, al-Qaeda carried out several deadly attacks on US targets—including the 1998 embassy bombings in Kenya and Tanzania and the 2000 bombing of the USS Cole—killing hundreds of people.

Finland and Sweden joined NATO after Russia's invasion of Ukraine

In response to Russia's 2022 invasion of Ukraine, Finland and Sweden abandoned decades of military neutrality to join NATO, marking a major shift in Europe's security landscape and expanding the alliance to Russia's borders.

Watch Jon Stewart's unifying opening monologue during his first show back after the 9/11 terrorist attacks.

The 1941 Atlantic Charter was a World War II alliance and model for the UN

The Atlantic Charter was a pivotal 1941 agreement between Franklin D. Roosevelt and Winston Churchill, outlining shared goals for a post-World War II world rooted in freedom and self-determination. These ideals later inspired the founding principles of the United Nations.

AP Photos: 20 images documenting the enormity of 9/11

The Associated Press shares 20 photographers’ frames from Sept. 11, 2001, when hijackers crashed commercial planes into New York’s World Trade Center, the Pentagon and a Pennsylvania field.

The Cold War (1947-1991) prompted the birth of NATO and the Soviet Warsaw Pact

The geopolitical rivalry between the United States and Soviet Union was considered “cold" because the two countries never directly engaged in military combat during the time period. This page from the Kennedy Presidential Library outlines the causes and major events of the early Cold War.

A formal declaration of war automatically triggers hundreds of statutes granting the president sweeping domestic authority

Beyond authorizing military force abroad, a formal declaration activates a wide range of domestic powers, including authority over enemy property, trade restrictions, and emergency economic authority. It also waives the 60-day time limits under the War Powers Resolution.

How the NSA has changed through history

The National Security Agency was born in the Cold War and then transformed by 9/11. This article answers all the basic questions you might have about the NSA, from what it does to how much data it collects to some of its useful intercepts.

The National Security Council advises the president on foreign policy and national defense

Created in 1947, the NSC coordinates military, diplomatic, and intelligence policy matters. Chaired by the president, it includes key Cabinet officials and senior advisers who shape American responses to global crises and security threats.

Explore personal 9/11 oral histories from survivors, first responders, and families

The 9/11 Memorial Museum's archive includes over 3,500 firsthand interviews—spanning survivors, first responders, family members, and residents—offering rare, deeply personal perspectives on the tragedy and its aftermath.

Should the US have entered into World War I?

America entered World War I in 1917, but had remained neutral until that point. President Woodrow Wilson addressed Congress, further underlining the USA's neutrality. Eleven weeks later, he asked for a declaration of war. With attacks by German saboteurs on an American munitions depot, it seemed he had no choice. But did he? This article asks what might have happened if the US stayed out of WWI.

Hitler declared war on the United States four days after Pearl Harbor

Despite having no treaty obligation to join Japan’s fight, Hitler declared war on the US on Dec. 11, 1941. The move pulled America into the European theater and is widely seen as one of Hitler’s most strategic blunders.

Chernobyl pushed the world to create rapid-alert systems for nuclear accidents

In the aftermath of the disaster, nations adopted new agreements requiring immediate international notification of nuclear accidents. They coordinated emergency assistance—efforts led by the International Atomic Energy Agency to prevent future disasters from being concealed when radiation emergencies occur.

President George W. Bush learned of the 9/11 attacks while visiting a classroom.

Watch Springsteen open a somber 9/11 tribute

“America: A Tribute to Heroes” was a fundraising telethon on Sept. 21, 2001, and simulcast across the four major networks. Springsteen opened the program with “My City of Ruins,” a song originally written about Asbury Park that took on new significance after the Sept. 11 terrorist attacks.

Germany is pursuing its most significant military buildup since WWII.

The 9/11 plane crashes, which resulted in the collapse of the Twin Towers, created toxic dust that included materials including asbestos, silica, metals, concrete, and glass.