World War II

World War II began in Europe on September 1, 1939, when Germany invaded Poland. Great Britain and France responded by declaring war on Germany on September 3. The war between the U.S.S.R. and Germany began on June 22, 1941, with Operation Barbarossa, the German invasion of the Soviet Union. The war in the Pacific began on December 7/8, 1941, when Japan attacked the American naval base at Pearl Harbor and other American, Dutch, and British military installations throughout Asia.

The main combatants were the Axis powers (Germany, Italy, and Japan) and the Allies (France, Great Britain, the United States, the Soviet Union, and, to a lesser extent, China).

The Allied powers were led by Winston Churchill (United Kingdom); Joseph Stalin (Soviet Union); Charles de Gaulle (France); and Franklin D. Roosevelt and Harry S. Truman (United States). The Axis powers were led by Adolf Hitler (Germany), Benito Mussolini (Italy), and Hideki Tojo (Japan).

The war in the Pacific turned against Japan during the Battle of Midway (June 3–6, 1942), an American victory that destroyed the Japanese first-line carrier force and, together with the Battle of Guadalcanal, ended Japan’s ability to prosecute an offensive war.

The tide of the war in Europe shifted with the Soviet victory at the Battle of Stalingrad (February 1943). More than one million Soviet troops and tens of thousands of civilians died in the defense of the city, but the destruction of two entire German armies marked the beginning of the end of the Third Reich.

The Allied landings at Normandy on June 6, 1944, opened a second front in Europe, and Germany’s abortive offensive at the Ardennes in the winter of 1944–45 marked the Third Reich’s final push in the west. The Red Army advanced from the east and effectively claimed all the territory under its control for the Soviet sphere. The Allied armies converged on Berlin. Adolf Hitler committed suicide on April 30, 1945, and the war in Europe ended on May 8.

The American “island hopping” campaign had destroyed key Japanese installations throughout the Pacific while allowing bypassed islands to wither on the vine. Hundreds of thousands were killed in firebombings of Japanese cities, and the atomic bombings of Hiroshima and Nagasaki in August 1945 knocked Japan out of the war.

Estimates of the total number of people killed during World War II have ranged from 35,000,000 to 60,000,000—a significant span, because statistics about the war’s casualties are inexact. The Soviet Union and China are believed to have suffered the most total casualties, while an estimated 5,800,000 Poles died, which represents about 20 percent of Poland’s prewar population. About 4,200,000 Germans died, and about 1,972,000 Japanese died. In all, the scale of human losses during World War II was vast. A table that details estimated deaths by country is available here.