September 1–27, 1939 · Eastern Europe Theater▶ Animated map

Germany invaded Poland from the west on September 1st with 1.5 million troops, using Blitzkrieg — coordinated tanks, motorized infantry, and dive bombers — to shatter Polish defenses. On September 17th, the Soviet Union invaded from the east under the secret Molotov-Ribbentrop Pact. Warsaw surrendered September 27th. Poland was divided between Nazi Germany and the Soviet Union.

September 3, 1939 – May 8, 1945 · Atlantic Theater▶ Animated map

The longest continuous military campaign of WWII. German U-boats waged unrestricted submarine warfare against Allied shipping, threatening to starve Britain into submission. In 1942 alone, U-boats sank over 1,600 Allied ships. The Battle of the Atlantic turned in May 1943 — 'Black May' — when improved radar, long-range aircraft, escort carriers, and cracked Enigma codes allowed the Allies to destroy 41 U-boats in a single month. Dönitz withdrew his fleet. Allied supply lines were never again seriously threatened.

May 10 – June 25, 1940 · Western Europe Theater▶ Animated map

Germany bypassed France's Maginot Line by driving armored columns through the 'impassable' Ardennes Forest, cutting Allied forces in two. 338,000 Allied troops were evacuated from Dunkirk in a desperate naval operation using everything from destroyers to fishing boats. France signed an armistice on June 22nd; Paris fell without a fight. In six weeks Germany had done what it couldn't do in four years of WWI.

June 10, 1940 – May 13, 1943 · North Africa Theater▶ Animated map

A see-saw campaign across the North African desert lasting nearly three years. Rommel's Afrika Korps nearly captured the Suez Canal before being halted at El Alamein. Montgomery's victory at El Alamein in November 1942 was the first major British land victory of the war. American forces landed in Operation Torch; the Axis forces were squeezed from both sides and surrendered in Tunisia in May 1943.

July 10 – October 31, 1940 · Western Europe Theater▶ Animated map

The first major campaign fought entirely by air forces. The Luftwaffe attempted to destroy the RAF as a prelude to Operation Sea Lion — the invasion of Britain. RAF Fighter Command, using radar and the Spitfire and Hurricane, inflicted unsustainable losses. When Hitler shifted attacks to bombing London (the Blitz), it gave RAF airfields time to recover. Germany never achieved air superiority.

June 22 – December 5, 1941 · Eastern Front Theater▶ Animated map

The largest military operation in history — 3.8 million Axis troops invaded the Soviet Union on a 1,800-mile front. Three army groups drove toward Leningrad, Moscow, and Kiev. Soviet forces collapsed in catastrophic encirclements; 3.5 million Soviet soldiers were captured in the first five months. But the vast distances, early winter, and fierce Soviet resistance slowed the advance. German forces were stopped short of Moscow in December.

September 8, 1941 – January 27, 1944 · Eastern Front Theater▶ Animated map

German and Finnish forces encircled Leningrad on September 8, 1941, cutting off the city of 3 million. For 872 days the city endured. In the first winter, over one million civilians died of starvation — corpses lay in the streets, people ate wallpaper paste and leather. Supplies reached the city only across frozen Lake Ladoga, the 'Road of Life.' The city never surrendered. On January 18, 1943, a land corridor was broken through; on January 27, 1944, the siege was fully lifted.

December 7, 1941 · Pacific Theater▶ Animated map

Japan's surprise carrier-based air attack on the US Pacific Fleet at Pearl Harbor, Hawaii brought America into the war. 353 Japanese aircraft in two waves sank or damaged 19 ships (including 8 battleships), destroyed 188 aircraft, and killed 2,403 Americans. The three American aircraft carriers were at sea and survived.

February 8–15, 1942 · Pacific Theater▶ Animated map

Japanese General Yamashita led 70,000 troops down the Malay Peninsula on bicycles and in vehicles — a lightning 700-mile campaign in 55 days. Singapore's massive coastal guns pointed seaward; the Japanese came from the north, crossing the Strait of Johor on rafts and boats. British General Percival, with 130,000 troops, surrendered the island fortress on February 15 — the largest capitulation in British military history. Yamashita, who had only 30,000 men and was nearly out of ammunition, bluffed Percival into surrender.

June 4–7, 1942 · Pacific Theater▶ Animated map

The decisive naval battle of the Pacific war. American codebreakers had broken Japanese naval codes and knew the attack was coming. In a few critical minutes on June 4th, American dive bombers found the Japanese carriers refueling aircraft — decks covered in fuel hoses and ordnance — and sank four fleet carriers. Japan lost Akagi, Kaga, Soryu, and Hiryu, along with hundreds of irreplaceable experienced aviators.

August 7, 1942 – February 9, 1943 · Pacific Theater▶ Animated map

The first major American offensive of the Pacific war. Marines landed on Guadalcanal on August 7 to capture a Japanese airfield — renamed Henderson Field. Six months of brutal land, air, and naval combat followed. Japan ran nightly supply convoys down 'the Slot' — called the Tokyo Express. The waters around the island became so littered with sunken ships they were named 'Ironbottom Sound.' Japan lost over 600 aircraft and most of its experienced naval aviators. In February 1943, Japan evacuated its surviving troops in secret.

August 23, 1942 – February 2, 1943 · Eastern Front Theater▶ Animated map

The most destructive battle in human history. Germany's 6th Army fought its way into Stalingrad in brutal street-by-street, building-by-building combat. Soviet General Zhukov then launched Operation Uranus, encircling the entire 6th Army. Hitler refused to allow a breakout. Paulus's 300,000 men slowly starved and froze through the Russian winter. On February 2nd, 1943, 91,000 survivors surrendered.

July 4–23, 1943 · Eastern Front Theater▶ Animated map

The largest tank battle in history — over 6,000 tanks on both sides. Germany's Operation Citadel aimed to eliminate the Kursk salient and regain the initiative. Soviet intelligence had obtained the German plans; Zhukov built massive defensive belts and waited. The German attack stalled in deep Soviet defenses. The Soviets then launched their own massive counteroffensives, beginning the great drive westward.

July 9, 1943 – May 2, 1945 · Mediterranean Theater▶ Animated map

Allied forces invaded Sicily on July 9, 1943, then crossed to the Italian mainland in September. Mussolini was deposed and Italy surrendered, but Germany occupied and fiercely defended the peninsula. Kesselring conducted a masterful fighting withdrawal through a series of defensive lines — the Winter Line, Gustav Line, Gothic Line — forcing the Allies to fight for every mountain and river. The battles at Monte Cassino, Anzio, and the Gothic Line ground on for nearly two years. Germany surrendered in Italy on May 2, 1945.

June 6, 1944 · Western Europe Theater▶ Animated map

The largest amphibious invasion in history. 156,000 Allied troops landed on five Normandy beaches — Utah, Omaha, Gold, Juno, Sword — supported by 11,000 aircraft and 7,000 naval vessels. Omaha Beach saw the bloodiest fighting; American troops were cut down in the surf under withering German fire. By nightfall the Allies had established a beachhead. The liberation of Western Europe had begun.

September 17–25, 1944 · Western Europe Theater▶ Animated map

Montgomery's bold plan to end the war by Christmas: drop three airborne divisions behind German lines to seize key bridges in the Netherlands, then rush armored columns up a single highway to cross the Rhine at Arnhem. The first two bridges were taken; at Arnhem, the British 1st Airborne Division landed near two SS Panzer divisions resting after Normandy. 'A bridge too far' — the division was destroyed; the Rhine crossing failed.

December 16, 1944 – January 25, 1945 · Western Europe Theater▶ Animated map

Germany's last major offensive in the West. Through fog and overcast that grounded Allied air power, three German armies attacked through the Ardennes, creating a 'bulge' in Allied lines and nearly splitting them. American forces were encircled at Bastogne; General McAuliffe's reply to German demands for surrender was a single word: 'NUTS!' When the weather cleared, Allied air power destroyed the German spearheads.

February 19 – March 26, 1945 · Pacific Theater▶ Animated map

US Marines landed on a volcanic island defended by 22,000 Japanese troops in an elaborate network of tunnels, bunkers, and caves. General Kuribayashi's strategy was to inflict maximum casualties rather than defend the beaches. The Marines fought yard by yard through the underground defenses. The iconic flag-raising on Mount Suribachi was captured in the war's most famous photograph. Of the 22,000 Japanese defenders, only 216 survived.

April 1 – June 22, 1945 · Pacific Theater▶ Animated map

The largest amphibious assault in the Pacific war — 180,000 US troops landing on an island within aircraft range of Japan's home islands. Japanese General Ushijima did not defend the beaches; instead he fortified the island's rugged interior with 120,000 troops and a network of caves, pillboxes, and tunnels. Kamikaze aircraft sank 36 US ships and damaged 368 more — the greatest naval losses of the entire Pacific war. The battle lasted 82 days of relentless combat in rain-soaked terrain. Gen. Buckner was killed on June 18, just days before the island fell. Ushijima performed ritual suicide.

April 16 – May 2, 1945 · Eastern Front Theater▶ Animated map

The final battle of the European war. 2.5 million Soviet troops with 6,000 tanks converged on Berlin. Hitler refused to leave his underground bunker as the city burned around him. On April 30th he committed suicide. Soviet soldiers raised the Red Flag over the Reichstag. On May 2nd the Berlin garrison surrendered; V-E Day followed on May 8th.

August 6 & 9, 1945 · Pacific Theater▶ Animated map

The B-29 Enola Gay dropped 'Little Boy' on Hiroshima on August 6th, instantly killing 70,000–80,000 people; tens of thousands more died later from radiation. 'Fat Man' fell on Nagasaki three days later, killing 40,000 immediately. Japan announced surrender on August 15th. The formal surrender ceremony was held September 2nd on the deck of USS Missouri in Tokyo Bay.