8.8 World War II

Germany's Blitzkrieg, or lightning war, combined tanks, motorized infantry and dive-bombers, coordinated by radio, to punch through enemy lines and encircle armies before they could react. Poland fell in about five weeks in 1939, with the Soviet Union invading from the east under the Nazi-Soviet Pact. In spring 1940 Germany took Denmark and Norway, then attacked the Netherlands, Belgium and France on May 10. German tanks went around the Maginot Line through the Ardennes forest. More than 330,000 British and French troops were evacuated from Dunkirk, and France signed an armistice on June 22, 1940. Germany occupied northern France, and a collaborating government under Marshal Pétain ruled the south from Vichy. Charles de Gaulle led the Free French from London.

Britain, now led by Winston Churchill, fought on alone. In the Battle of Britain (summer and autumn 1940), the Royal Air Force, helped by radar, defeated the German air force's attempt to gain control of the skies, forcing Hitler to postpone invasion. German bombing of British cities, the Blitz, continued into 1941.

On June 22, 1941, Germany launched Operation Barbarossa, the invasion of the Soviet Union, with about three million German troops, plus allied forces. It aimed to destroy communism and seize land and resources for German settlers. German armies reached the outskirts of Moscow and besieged Leningrad, where about a million civilians died during a siege of nearly 900 days, but the Soviets stopped them before Moscow in December 1941. Meanwhile, Japan, which had been at war in China since 1937, attacked the U.S. fleet at Pearl Harbor on December 7, 1941, and swept across Southeast Asia and the Pacific. Hitler declared war on the United States four days later.

• Stalingrad (August 1942–February 1943): the Soviets trapped and destroyed the German Sixth Army, with nearly 300,000 German and allied soldiers caught in the pocket; afterward the Red Army mostly advanced, winning the huge tank battle of Kursk (July 1943).
• North Africa and Italy: British forces won at El Alamein (late 1942), the Allies invaded Sicily and Italy in 1943, and Mussolini was overthrown.
• D-Day (June 6, 1944): American, British, Canadian and other Allied troops landed in Normandy, opening a second front in the west; Paris was liberated in August.
• Germany's defeat: Soviet troops took Berlin, Hitler killed himself on April 30, and Germany surrendered unconditionally on May 8, 1945.
• Japan's defeat: after the United States dropped atomic bombs on Hiroshima (August 6) and Nagasaki (August 9), and the Soviet Union declared war on Japan, Japan surrendered in August 1945, signing on September 2.

• The Soviet Union's all-out commitment: most German military deaths came on the Eastern Front, and roughly 27 million Soviet citizens died.
• American and British industry: the U.S. out-produced the Axis in planes, tanks and ships and supplied its allies through Lend-Lease (1941).
• Science and technology: radar, British codebreaking of German Enigma messages at Bletchley Park, mass-produced penicillin, and the atomic bomb built by the Manhattan Project with British and European émigré scientists.
• Cooperation and leadership: the Allies coordinated strategy at conferences such as Tehran (1943), and Churchill's speeches sustained British morale.
• Resistance: civilians and partisans in occupied Europe sabotaged, spied and fought, including the French Resistance, Tito's Yugoslav Partisans and the Polish Home Army's Warsaw Uprising (1944).

World War II was the deadliest conflict in history, with estimates of total deaths commonly exceeding 60 million, most of them civilians. Industrialized warfare reached new extremes: the bombing of cities such as Coventry, Hamburg and Dresden, the Holocaust (8.9), and finally nuclear weapons, which began an era of nuclear arms races in which a single war could destroy whole countries (9.3). The war killed a huge share of a generation of Soviet and German men, forced millions to flee or be expelled from their homes, and weakened old class hierarchies as whole societies sacrificed together.