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

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

Soviet control spread across Eastern Europe after WWII

In the late 1940s, the USSR solidified control over Eastern Europe by installing pro-communist regimes in countries like Poland, Hungary and Romania—often through rigged elections and political repression.

The Nazis and Soviets agreed to a non‑aggression pact in 1939

On August 23, 1939, Nazi Germany and the Soviet Union signed the Molotov–Ribbentrop Pact—a public commitment to not attack each other combined with a secret agreement dividing Eastern Europe into spheres of influence. This pact enabled Germany to invade Poland unopposed from the east and delayed conflict with the USSR until June 1941.

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.

The Soviet Union consisted of 15 Soviet Socialist Republics

The USSR comprised 15 republics—Armenia, Azerbaijan, Belarus, Estonia, Georgia, Kazakhstan, Kyrgyzstan, Latvia, Lithuania, Moldova, Russia, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan—all governed from Moscow, the Soviet capital and still Russia’s capital today.

The Soviet Union had a similar sphere of influence policy during the Cold War—the Brezhnev Doctrine

Articulated in 1968, the Brezhnev Doctrine claimed the Soviet Union's right to intervene militarily in its satellite states to prevent any deviation from communist rule. It was used to justify the invasion of Czechoslovakia that same year and the invasion of Afghanistan in 1979.

Wartime conferences exposed cracks in the US–Soviet alliance

At the Tehran, Yalta and Potsdam Conferences, Allied leaders coordinated WWII strategy—but deep disagreements over postwar Europe foreshadowed the Cold War. The USSR’s push for influence in Eastern Europe clashed with US and British calls for self-determination.

During the Cold War, the rules-based order was largely limited to the West

The Soviet Union and its allies operated outside the Bretton Woods institutions, meaning the postwar liberal order functioned as a regional rather than a truly global system. This changed with the USSR's collapse in 1991.

Communist governments across Eastern Europe fell in 1989

In 1989, a series of mostly peaceful uprisings led to the collapse of communist regimes in Eastern Europe. Protests and political shifts in countries like Poland, East Germany and Czechoslovakia marked the end of Soviet dominance in the region.

Churchill’s 1946 ‘Iron Curtain’ speech warned of growing Soviet domination

In a 1946 speech, Winston Churchill declared that an “Iron Curtain” had descended across Europe—dividing East from West. The address marked one of the first public acknowledgments of the emerging Cold War and coined the term that would define the conflict.

The Marshall Plan aimed to rebuild Europe and limit Soviet influence

Launched in 1948, the Marshall Plan provided over $12B (roughly $150B today) in US aid to help rebuild Western Europe. While framed as economic recovery, it also served as a Cold War tool—tying countries to the US and excluding the Soviet bloc.

The Soviet Union explained

From 1922 to 1991, the Soviet Union spanned one-sixth of Earth’s landmass and housed nearly 300 million people. As the most significant test of Marxist governance, it sat at the center of the century’s defining struggle between capitalism and communism.

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

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.

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

NATO consists of 32 countries across North America and Europe.

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'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.

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.

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.

The Berlin Wall physically separated East and West Berlin for nearly three decades, preventing East Germans from fleeing to the West and earning the nickname 'the Iron Curtain.'

Germany is pursuing its most significant military buildup since WWII.

How Stalin, Roosevelt, and Churchill shaped the postwar world

The Yalta Conference was a pivotal 1945 meeting between Allied leaders that helped shape the postwar global order and laid the groundwork for the founding of the United Nations.

During the Cold War, the Soviet Union created a Eurovision competitor

The Soviet Union was not a member of the European Broadcasting Union, so it couldn't compete in Eurovision. In 1977, it turned a preexisting Polish-language singing competition into one that more closely resembled Eurovision and renamed it Intervision. The competition was open to countries from across the globe, regardless of their form of government, though most entrants were from communist countries.

Cold War rivalries fueled fierce competition in international sports

From Olympic medal counts to hockey showdowns, the US and USSR used sports to showcase ideological superiority. Athletic victories were framed as proof that each system—capitalist or communist—produced stronger, more disciplined citizens.

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 Soviet Union collapsed in 1991, due to economic decline and political unrest

By the late 1980s, the Soviet economy was stagnating and its political system was under tremendous strain. Soviet reforms failed to reverse the decline, and growing independence movements led to the USSR’s formal dissolution in 1991.

The Soviet Union’s surprising first atomic test ended the US nuclear monopoly

In 1949, the USSR successfully tested its first atomic bomb—ending the US monopoly on nuclear weapons and sparking an arms race that would define the Cold War.

Roosevelt formally recognized the Soviet Union in 1933

In 1933, President Franklin D. Roosevelt formally recognized the Soviet Union—ending 16 years of nonrecognition and aiming to improve trade and stabilize relations amid growing global instability.

The Truman Doctrine marked the start of US containment strategy

Introduced in 1947, the Truman Doctrine pledged US support for nations resisting communism—starting with Greece and Turkey—and launched the containment policy that defined early Cold War strategy.

The US and the USSR each boycotted Olympic Games during the Cold War

The US led a boycott of the 1980 Moscow Olympics over the Soviet invasion of Afghanistan. In retaliation, the USSR and its allies skipped the 1984 Los Angeles Games.

See an animated map of the entire Cold War.

Explore a timeline tracing the Soviet Union’s collapse from 1985 to 1991

This interactive webpage charts the USSR’s final years—from Gorbachev’s rise to the 1991 dissolution—using infographics, key quotes, and profiles of prominent political figures to explain how the Soviet state unraveled, and Russia emerged in its place.

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.

Learn how the Soviets won the early space race

This video traces how Cold War arms competition transformed rocketry into a symbol of global power, following pioneers like Tsiolkovsky and von Braun through World War II and into the 1950s, culminating in the Soviet Union’s launch of Sputnik I in 1957.

A 1983 NATO war simulation provoked the Soviets to prepare for war

The "SNAFU" podcast, hosted by actor and comedian Ed Helms, explores some of the biggest blunders in history. Season one focuses on the 1983 NATO Able Archer military exercise, a war game that simulated nuclear attacks on the Soviet Union. The USSR mistook the exercise for a genuine threat and prepared its forces for war. Helms recounts this almost catastrophic event in world history with his signature humor.

Sartre eventually denounced communism

The French philosopher was a long-time ardent supporter of communism and the USSR. He finally spoke out against the movement with the 1956 Soviet invasion of Hungary, saying that the move was "made possible by 12 years of terror and imbecility."

The USSR launched the world's first satellite, Sputnik 1, into space in 1957

Sputnik, launched by the Soviet Union in 1957, became the world's first artificial satellite. While the technology itself was limited, the launch ignited the space race and signaled that intercontinental missiles and space technology had arrived faster than American leaders expected.

Economic stagnation and the arms race pushed the USSR toward collapse

By the 1980s, chronic economic stagnation and soaring military costs forced Gorbachev to launch sweeping reforms—perestroika and glasnost—to revive the Soviet system. Instead, openness fueled independence movements across the republics, accelerating the regime’s rapid downfall.

Propaganda became a key weapon in the US–Soviet Cold War

Both superpowers waged a global battle for hearts and minds through propaganda—using film, radio, art and education to promote their values. The US emphasized freedom and prosperity, while the USSR championed socialism and anti-imperialism.

During the Cold War and into the 21st century, US and Soviet/Russian leaders repeatedly agreed to arms control treaties, though strained tensions have led to the expiration of agreements in recent years.

The USSR's space program achieved many historic firsts in the Space Race

Soviet scientists launched the first satellite, sent the first human into orbit, and carried out early spacewalks—milestones that gave the USSR a decisive early lead in the Space Race and reshaped global competition in science and technology.

US–Soviet hostility began long before the Cold War

US–Soviet tensions began decades before WWII. After the 1917 revolution, the US refused to recognize the Bolshevik regime and even sent troops to fight against it.

Ukraine's Soviet Republic was tightly bound to Moscow's control

Proclaimed in 1917 and absorbed into the USSR in 1922, the Ukrainian Soviet Socialist Republic was nominally independent yet operated under Moscow's control, with its government and laws directed by the Soviet Communist Party.

Relationships between countries have become more peaceful since the rules-based order was established

Our World in Data monitors bilateral relationships on a spectrum from open rivalry to "positive peace"—deep cooperation and mutual protection. In 1945, no countries had highly cooperative security relationships. Today, nearly a fifth do.

The bizarre 1920 proposal to form a pizza-shaped central European state

In light of the challenges of the Treaty of Versailles, which concluded the Great War, a mostly unknown author, and son of the map's printer, PA Maas suggested central Europe be integrated into a single state. With a central capital in Vienna, 24 Kantons, or regions, would radiate outward in pie-slice shapes.

Questions about the US' commitment to its allies may have sparked a new nuclear age

Some US allies—from Warsaw to Seoul—are reevaluating their security amid doubts over American nuclear commitment, signaling the possibility they may want to acquire their own weapons.

NASA was created in 1958 in the wake of the Sputnik 1 launch

The launch of Sputnik 1 in 1957 jolted US political leaders, who urgently consulted scientists and defense experts on how to respond. Concerns about Soviet technological dominance—and the promise of civilian space applications—led directly to NASA’s creation in 1958.

Explore 100 years of communism across the globe, from the 1917 October Revolution to North Korea's modern nuclear defiance.