World War II, lasting from 1939 to 1945, involved most of the world in a conflict between the Axis and Allied powers. This guide covers foundational dates, key terms, and major events in both European and Pacific theaters. Understanding WWII helps you grasp 20th-century history and the modern world's origins.
World War II began September 1, 1939 when Germany invaded Poland. The European Theater involved Nazi Germany's expansion across Europe under Adolf Hitler's leadership. The Blitzkrieg or lightning war tactics enabled rapid German conquests of France, the Low Countries, and Eastern European nations.
Key events included the Battle of Britain 1940 where British defense stopped German invasion, Operation Barbarossa 1941 where Germany invaded the Soviet Union, and D-Day June 6, 1944 when Allies invaded Normandy. The Holocaust occurred during this period as Nazis systematically murdered six million Jews in concentration camps and death camps.
The Nazi ideology emphasized racial supremacy and totalitarianism. The Nuremberg Trials after the war prosecuted Nazi leaders for war crimes and established precedent for international justice for violations of humanity.
The Pacific War began December 7, 1941 with Japan's attack on Pearl Harbor, killing over 1,100 American servicemen and prompting US entry into World War II. Japan had been expanding militarily since 1937, invading Manchuria and China. The Pacific War featured different tactics than Europe, with island hopping strategy where Americans captured islands toward Japan rather than invading every Japanese position.
Major battles included Midway 1942 as a turning point against Japanese, Iwo Jima and Okinawa 1945 as final approaches to Japan. The war ended when atomic bombs destroyed Hiroshima and Nagasaki in August 1945, prompting Japan's unconditional surrender September 2, 1945.
Japanese militarism and expansionism in Asia caused extensive casualties among Chinese and other Asian populations, with war crimes like the Rape of Nanking representing atrocities comparable to European theater.
World War II affected civilians as much as soldiers through rationing of food and resources, bombing of cities, and forced relocations. In America, women worked in factories as Rosie the Riveter, supporting war production. Japanese Americans were controversially interned through Executive Order 9066 for over a year. The Tuskegee Airmen, African American pilots, broke racial barriers while fighting enemy aircraft.
The war led to the founding of the United Nations in 1945 to prevent future world wars. The Yalta and Potsdam Conferences among Allied leaders shaped post-war arrangements, with growing tensions between the Soviet Union and Western powers. This led to the Cold War that lasted until 1991.
WWII ended European colonialism, created two superpowers, and reshaped international relations. The Holocaust and Nuremberg Trials established new standards for human rights and war crimes accountability.
WWII resulted from unresolved tensions after WWI, the Great Depression economic crisis, and the rise of fascism in Germany, Italy, and Japan. Germany sought to overturn the Treaty of Versailles by expanding territory and establishing racial supremacy.
The Holocaust was Nazi Germany's systematic genocide of six million Jews during WWII. It also targeted Roma people, disabled individuals, political prisoners, and others deemed inferior by Nazi racial ideology. It represents one of history's greatest atrocities.
The US entered WWII after Japan attacked Pearl Harbor on December 7, 1941. The surprise attack killed over 1,100 American servicemen and prompted Congress to declare war the next day. The US had been providing aid before official entry.
WWII established two superpowers (US and Soviet Union), ended European colonialism, created the United Nations, sparked the Cold War, and fundamentally reshaped international relations and human rights standards.