The Second World War

The Great Depression that began in 1929 brought mass unemployment and made extremist movements more attractive. In Germany, Adolf Hitler's Nazi Party came to power in 1933, destroyed democratic institutions, persecuted Jews and political opponents, and rearmed in defiance of the Treaty of Versailles.

Fascist Italy invaded Ethiopia, and Japan, dominated by militarists, invaded Manchuria in 1931 and began full-scale war with China in 1937. Britain and France pursued appeasement, accepting Germany's annexation of Austria and, at Munich in 1938, of the Sudetenland in Czechoslovakia. In August 1939 Germany and the Soviet Union signed a non-aggression pact that secretly divided Eastern Europe between them.

Germany invaded Poland on 1 September 1939, and Britain and France declared war two days later. In spring 1940 German forces overran Denmark, Norway, the Netherlands, Belgium and France using fast combined attacks of tanks and aircraft.

Britain, led by Winston Churchill, fought on. The Royal Air Force defeated the German air campaign in the Battle of Britain in 1940, preventing an invasion. In June 1941 Germany broke its pact and invaded the Soviet Union, opening the largest land campaign in history.

On 7 December 1941 Japan attacked the American fleet at Pearl Harbor and struck across Southeast Asia and the Pacific. The United States entered the war against Japan and, after Hitler declared war on it, against Germany as well.

The tide turned in 1942 and 1943. The US Navy defeated Japan at Midway in June 1942. The Soviet victory at Stalingrad, where a German army surrendered in February 1943, was a decisive defeat for Germany. British and Commonwealth forces won at El Alamein in North Africa, and the Allies went on to invade Italy.

Nazi Germany carried out the systematic murder of about six million Jews, roughly two thirds of Europe's Jewish population. Victims were shot in mass executions in Eastern Europe and deported to extermination camps such as Auschwitz-Birkenau and Treblinka, where they were killed in gas chambers.

The Nazis also murdered Roma, disabled people, Soviet prisoners of war, Poles and others. The Holocaust led to the legal concept of genocide and shaped the development of international human rights law after the war.

• On 6 June 1944, D-Day, Allied forces landed in Normandy and began liberating Western Europe.
• Soviet offensives drove German forces back across Eastern Europe toward Berlin.
• Hitler killed himself in Berlin on 30 April 1945, and Germany surrendered unconditionally on 8 May 1945.
• The United States dropped atomic bombs on Hiroshima on 6 August and Nagasaki on 9 August 1945, and the Soviet Union declared war on Japan.
• Japan announced its surrender on 15 August and signed the formal surrender on 2 September 1945.

Estimates of total deaths range from about 70 to 85 million people, most of them civilians. The Soviet Union and China suffered the largest losses. Cities across Europe and Asia lay in ruins, and millions of people were displaced.

The United Nations was founded in 1945, and war crimes trials at Nuremberg and Tokyo held leaders to account. The United States and the Soviet Union emerged as superpowers, Europe was divided, and the rivalry between them became the Cold War. Weakened colonial powers soon faced independence movements across Asia and Africa.