World War II
1939 — 1945

Historians trace the war's roots to the very treaty that closed the last one. The 1919 Treaty of Versailles imposed crushing reparations on Germany, redrew borders, and left whole populations resentful. The interwar order, designed for stability, proved brittle.

The Great Depression of 1929 wiped out savings, collapsed trade, and shattered faith in liberal democracy. Mass unemployment opened the door to radical movements. In Italy, Mussolini consolidated fascist rule by 1925; in Germany, Hitler and the Nazi Party seized power in 1933 on a platform of grievance, racial nationalism, and rearmament.

The League of Nations, lacking American membership and military teeth, watched Japan invade Manchuria (1931), Italy seize Ethiopia (1935), and Germany remilitarize the Rhineland (1936). Appeasement at Munich (1938) yielded the Sudetenland; six months later Hitler took the rest of Czechoslovakia.

By August 1939 the Nazi-Soviet Pact had carved Eastern Europe into spheres. The fuse was lit.

At 4:45 a.m. on September 1, 1939, German forces crossed the Polish border under cover of staged provocations. Stuka dive-bombers struck airfields; panzer divisions broke through cavalry and infantry lines in days. The world's first true demonstration of Blitzkrieg — lightning war — left Warsaw under siege within weeks.

Two days later, on September 3, the United Kingdom and France declared war on Germany. Australia, New Zealand, and the Dominions followed within hours. On September 17, the Soviet Union invaded Poland from the east, fulfilling the secret protocol of the Molotov-Ribbentrop Pact. Poland was partitioned by month's end.

The war in the West then entered the so-called "Phoney War" — eight months of static frontiers while Hitler prepared his next strike.

On June 22, 1941, Germany launched Operation Barbarossa — the largest land invasion in history. Three million Axis troops crossed a 1,800-mile front into the Soviet Union. Initial gains were staggering; entire Soviet armies were encircled. By December the Wehrmacht was within sight of Moscow's spires.

Then winter, exhausted supply lines, and Soviet reserves from Siberia stopped the advance. The Red Army counterattacked on December 5. The war Hitler had counted on winning in months would now be measured in years.

Two days later, on December 7, Japanese carrier aircraft struck the U.S. Pacific Fleet at Pearl Harbor, Hawaii — "a date which will live in infamy." More than 2,400 Americans were killed; eight battleships were hit. Japan simultaneously attacked Malaya, Hong Kong, the Philippines, and Wake.

On December 8 the United States declared war on Japan. On December 11, Germany and Italy declared war on the United States. The world's three largest economies were now at war on the same side.

Hitler ordered the German Sixth Army to seize Stalingrad in summer 1942 for its industries, its symbolic name, and its position on the Volga. House-to-house fighting reduced the city to rubble; rifle squads contested staircases for weeks. The Soviet defenders held a sliver of the western bank and bled the attackers dry.

On November 19, Operation Uranus encircled the Sixth Army with two pincer thrusts. Hitler forbade breakout. By February 2, 1943, Field Marshal Paulus surrendered with the remnants — some 91,000 men, of whom only a few thousand would see Germany again.

The Eastern Front absorbed roughly three-quarters of German casualties. From Kursk (1943, the largest tank battle in history) onward, the Red Army drove west — through Ukraine, Belarus, Poland — toward Berlin.

The Nazi regime carried out the systematic, state-organized persecution and murder of approximately six million Jews — roughly two of every three Jews in Europe. The genocide began with discrimination, expropriation, and ghettoization in the 1930s; escalated to mass shootings by Einsatzgruppen in occupied Soviet territory after 1941; and culminated in the death camps — Auschwitz, Treblinka, Sobibor, Belzec, Majdanek, Chelmno — where industrial gas chambers operated on a continental scale.

Roma and Sinti, Soviet POWs, Poles, the disabled (murdered under "Aktion T4"), political dissidents, gay men, Jehovah's Witnesses, and others were targeted as well. The total Nazi-era civilian death toll runs to roughly eleven million.

Allied forces liberating camps in 1944–45 documented what they found in photographs and film. The Nuremberg trials (1945–46) prosecuted leading perpetrators and helped establish the modern category of "crimes against humanity." Survivors built memory institutions — Yad Vashem, the USHMM, archives across Europe — to ensure the historical record could not be denied.

For more than two years the Western Allies built up forces in southern England under General Dwight D. Eisenhower. Deception — Operation Bodyguard, dummy armies, false radio traffic — convinced German command to expect the blow at Calais.

Just after midnight on June 6, 1944, paratroopers of the U.S. 82nd and 101st Airborne and the British 6th Airborne Division dropped behind the lines. At dawn, infantry of five nations stormed five Normandy beaches: Utah, Omaha, Gold, Juno, and Sword. Omaha, against the cliffs, cost the most.

By nightfall the beachhead held. Within ten weeks Allied armies broke out at Saint-Lô, raced across France, and entered a liberated Paris on August 25. Brussels fell on September 3. The road east led, slowly, to the Rhine.

By April 1945 the Red Army had reached Berlin from the east; American and British forces were across the Rhine in the west. On April 30, with Soviet shells falling on the Reich Chancellery, Adolf Hitler took his own life in the Führerbunker. On May 7 General Jodl signed the unconditional surrender at Reims; on May 8 — V-E Day — cities across Europe filled with crowds.

The Pacific war continued. After bloody campaigns at Iwo Jima and Okinawa — foreshadowing the cost of any invasion of Japan — the United States used atomic weapons developed under the Manhattan Project. Hiroshima was struck on August 6, Nagasaki on August 9. Tens of thousands died instantly; many more from injuries and radiation in the months and years that followed.

The Soviet Union declared war on Japan and invaded Manchuria on August 8–9. On August 15 Emperor Hirohito announced surrender. The instrument was signed aboard the USS Missouri in Tokyo Bay on September 2, 1945 — V-J Day. The war was over.