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

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.

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.

How NATO responded to 9/11

The collective defense clause of the NATO constitution has only been invoked one time: after the 9/11 terrorist attacks against the United States. This video explores the immediate actions NATO took to respond to the attacks to support the United States. These firsthand clips from 2001 give a sense of the magnitude of the moment and the difficult decisions facing NATO leaders at the time.

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.

How NATO works

NATO now includes 32 member nations—but how does the alliance actually function? This explainer breaks down its structure, decision-making process, and funding model. From its founding in 1949 to its collective response after 9/11, here’s how NATO operates on a global scale.

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.

NATO was formed in 1949 to deter Soviet expansion and integrate Europe

Europe was in shambles after World War II, which saw 36 million Europeans killed, and the Soviets were looking to increase their influence. Beyond deterring the Soviets, the alliance sought to restore Europe and prevent nationalist militarism akin to the German Nazis and Italian Fascists.

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.

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.

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.

The 1955 Warsaw Pact was the Soviet Union’s answer to NATO

The pact included Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania, and the USSR. The pact established collective security and a joint military command between the member countries.

The threat of nuclear annihilation reshaped global diplomacy

The first use of atomic weapons introduced the possibility of a war with no survivors. This article examines how nuclear fear shaped Cold War diplomacy and continues to influence international relations today.

The Non‑Proliferation Treaty was designed to prevent new states from developing nuclear bombs

The Treaty on the Non‑Proliferation of Nuclear Weapons (created in 1968, effective 1970) binds non-nuclear states to forgo nuclear weapons and commits nuclear powers to share peaceful technology and pursue disarmament—forming the core of the global non-proliferation regime.

War-making authority is divided between Congress and the president in the Constitution

Article I grants Congress the power to declare war and fund the military, while Article II makes the president commander in chief. However, the Constitution does not clearly delineate where one authority ends and the other begins, creating a tension that has never been fully resolved.

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.

The Articles of Confederation were not a federal system

Ratified in 1781, the Articles of Confederation left the states sovereign and independent, denied the national government power to tax or regulate commerce, and forced Congress to act through the states—exposing the limits of confederation and paving the way for US federalism.

The GATT and its successor, the WTO, were established to lower trade barriers

Signed in 1947, the General Agreement on Tariffs and Trade began systematically reducing tariffs and trade barriers among member nations. In 1995, it was replaced by the World Trade Organization, which expanded those rules and established a formal dispute settlement system.

The Declaration was a calculated appeal for foreign allies

This article argues that the Declaration of Independence wasn’t just a statement of separation from Britain. It was a strategic message aimed at France and Spain, designed to secure military support against the far stronger British Empire.

The 1951 Refugee Convention established international refugee rights and state obligations amid mass World War II displacement

The international treaty defines refugee status and outlines refugees' entitled rights while establishing state obligations to protect them. The UNHCR explains the convention's significance in creating the legal framework governing refugee protection worldwide.

The global defense industry in one chart

The world's most valuable defense companies (for example, Lockheed Martin) make up much of the global defense industry. As of 2025, RTX led the pack with a roughly $183B market cap.

The Arab League has 22 members and very little enforcement power

It was founded in Cairo in 1945 and spans 22 nations across the Middle East and North Africa, ostensibly to coordinate policy on economics, culture, and defense. Its charter says any resolution only binds states that voted for them, rendering most of them toothless.

Five key causes of World War I

What caused World War I? The ready answer refers to the assassination of Archduke Franz Ferdinand. But there was more to it than that. This article, accompanied by a short explanatory video, outlines how mutual defense alliances, imperialism, militarism, and nationalism also had a heavy hand in the start of what some considered a "preventable war."

The Fifth Amendment covers a wide range of legal protections for those accused of a crime

While it is widely known for the right against self-incrimination, the Fifth Amendment also protects against being charged for the same crime twice, requires grand jury indictments for serious crimes, and mandates compensation when the government takes private property for public use.

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

Carl Jung proposed the controversial idea of the 'collective unconscious'

The famed psychologist proposed the idea in 1916, referring to a hypothetical universal part of the unconscious mind shared by all humans. It contains innate elements called archetypes—such as the Hero, the Mother, or the Shadow—that shape human behavior, dreams, and myths across cultures.

The “Phoney War” was an eight‑month build-up to war

From September 1939 to May 1940, following their war declaration on Germany, Britain and France entered a phase of military inaction—even as civil defence measures, naval blockades, and rationing intensified at home. Skirmishes were limited, but the decisive fighting didn't begin until Germany invaded Norway and France in April–May 1940, abruptly ending the uneasy stalemate.

Explore an interactive map of battles from the American Revolution, along with detailed summaries of each engagement

In 2025, four executives from large tech companies were given positions in the US Army Reserves—including Palantir Chief Technology Officer Shyam Sankar, which reinforced Palantir's ties with the US military and its role as a leading defense partner.

The idea for the Federal Reserve was conceived in secret in 1910—with bankers donning duck hunt gear for disguise while traveling to a remote country club on Georgia's Jekyll Island

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in terms of casualties, forces mobilized, and displacement of civilians.

American dance legend Martha Graham, sometimes called 'the Picasso of dance,' refused to perform at the 1936 Olympics in Berlin and conceived the piece 'Chronicle' in response to the experience.

The story of Dollree Mapp, whose legal challenge over her 1957 conviction for possessing "obscene material" led to a major strengthening of the Fourth Amendment

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

Famed poet TS Eliot rejected the manuscript for George Orwell's political fable 'Animal Farm,' writing that its criticism of authoritarianism was not 'the right point of view.'

The identity of the Tank Man in the iconic photo from the 1989 Tiananmen Square protests remains unknown and was possibly killed.

View the ten deadliest tornadoes in US history.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Art theft is the third-largest source of criminal revenues worldwide, thanks in part to the subjective nature of valuing a work of art.

The Brothers Grimm were lawyers before they were storytellers, and became interested in fairy tales as they began investigating how rules and customs had been passed down through cultures.

Calculate how much of your tax dollars go to each federal program based on your income, filing status, and number of children

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Prince's sexually explicit 1984 track 'Darling Nikki' attracted the ire of the Parents Music Resource Center, an advocacy group that inspired the Parental Advisory sticker, even though the song ends with a Christian message.

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.