European leaders pursued appeasement of Hitler in the 1930s, hoping to avoid war.

Germany’s invasion of Poland in 1939 launched World War II

On September 1, 1939, Nazi Germany launched a surprise invasion of Poland using blitzkrieg—coordinated air bombardments and armored assaults—to overwhelm Polish defenses within weeks. This lightning-strike strategy shocked the world and signaled both the start of World War II and a revolutionary shift in modern military tactics.

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.

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.

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.

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

Stalingrad was the turning point of WWII in Eastern Europe

The six-month siege (July 1942–February 1943) ended when the Soviet Union’s counteroffensive, Operation Uranus, encircled and destroyed Germany’s 6th Army. This decisive victory shifted momentum permanently to the Soviets on the Eastern Front, marking a major strategic reversal in Europe and undermining Nazi Germany’s war capacity.

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.

Hitler's 1941 invasion of the USSR doomed Nazi Germany

Hitler unleashed Operation Barbarossa on June 22, 1941, underestimating Soviet resilience, Russian winter, and logistics. His overconfidence—rooted in early victories like France—turned this campaign into a strategic catastrophe, shifting the war’s momentum irreversibly—often cited as his greatest blunder.

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 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.

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.

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 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.

Spies working on the Manhattan Project propelled the Soviet bomb program

Soviet infiltration—most notably by Klaus Fuchs—smuggled detailed implosion-design and hydrogen‑bomb data from Los Alamos to Moscow, cutting the USSR’s development time by at least a year and enabling their first atomic test in August 1949.

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.

The treaty that ended the First World War laid the groundwork for the Second.

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.'

The Nazi Party was founded in Germany in 1920 and tried a failed coup in 1923

Founded in Germany in February 1920, the National Socialist German Workers’ Party (Nazi Party) attempted its first major power grab in 1923 with the Beer Hall Putsch—a failed coup in Munich that killed about 16 Nazis and four police officers, led to Hitler’s arrest and treason trial, but ultimately elevated his public profile.

Champagne played a role in resisting the Nazis

When France surrendered to the Nazis in 1940, the invaders occupied the north. This was home to wine regions like Champagne and Bordeaux, which the Nazis were eager to loot. Winemakers took a stand by sheltering dissidents in their cellars, passing intelligence across borders, and even giving their lives to the cause.

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.

Germany is pursuing its most significant military buildup since WWII.

US secrets: Project Paperclip

The US launched Project Paperclip in 1946, covertly recruiting over 1,500 German scientists to advance American military and space programs. Among them was Wernher von Braun, a key architect of the V-2 rocket who later became instrumental in NASA’s Apollo missions. While these scientists accelerated technological breakthroughs, their recruitment raised moral debates about overlooking wartime affiliations in the name of progress—questions that remain unresolved today.

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.

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.

Germany’s surprise offensive in December 1944 failed to break Allied lines

In a bold counterattack from December 16, 1944, to January 28, 1945, Hitler committed over 400,000 troops in a surprise “Bulge” through the Ardennes forest in France. Although initially successful in creating a 50‑mile incursion, Allied defense halted the advance. German forces suffered irrecoverable losses (~100,000), while Allied casualties totaled ~75,000, marking the offensive as the last major German gamble and a decisive step toward Nazi defeat.

Before Pearl Harbor, the US was a nonbelligerent ally to the Allied powers

Between September 1940 and December 7, 1941, the United States remained officially neutral—yet President Roosevelt incrementally shifted policy from “cash‑and‑carry” to Lend‑Lease, funneling critical military aid to Britain and other allies without entering the war.

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

How the Great Depression and end of WWI paved the way for Hitler's rise to power

The end of WWI was triggered by an armistice that blamed the conflict on Germany and required the financially struggling country to pay reparations. This outraged nationalists and ignited conspiracies that Hitler was able to capitalize on, according to this six-minute video. It was during this financial strain that the Great Depression hit.

Meet the scientists who worked on the Manhattan Project.

The US space program was built on former Nazi expertise through Operation Paperclip

After WWII, the US secretly recruited over 1,600 German scientists, including ex-Nazis like Wernher von Braun. They repurposed V‑2 rocket technology to create NASA’s core capabilities—pivotal in the Saturn V and Apollo missions.

Worried that Nazi Germany could weaponize nuclear fission first, Albert Einstein wrote a 1939 letter warning President Roosevelt about the possibility of atomic bombs—a decision he later regretted.

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.

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 global nuclear arms regime has slowly eroded over the past few decades

Both Russia and the United States have withdrawn from key Cold War-era arms-control pacts. Russia's 2022 invasion of Ukraine marked a turning point, as it suspended its participation in inspections and data-sharing agreements.

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.

Some senior Nazis fled to South America and lived for decades

Using so-called "ratlines" through Spain, Italy, and into South American countries like Argentina, many of Adolf Hitler's closest associates evaded capture after the fall of Berlin in 1945. This video details the fate of eight, including infamous doctor Josef Mengele and logistics expert Adolf Eichmann.