World War II
Global conflict (1939–1945)
Cite this page
“World War II.” thisDay, thisday.info/history/world-war-ii/. Accessed 19 Oct. 2026.
World War II. (n.d.). thisDay. Retrieved October 19, 2026, from https://thisday.info/history/world-war-ii/
“World War II.” thisDay. Accessed October 19, 2026. https://thisday.info/history/world-war-ii/.
What was World War II?
World War II, or the Second World War (1 September 1939 – 2 September 1945), was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated. World War II was the deadliest conflict in history, causing the death of 60 to 75 million people. Millions died as a result of massacres, starvation, disease, and genocides, including the Holocaust. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes. The causes of World War II included unresolved tensions in the aftermath of World War I and the rise of fascism in Europe and militarism in Japan.
Background and consequences
Key events preceding the war included Japan's invasion of Manchuria in 1931, the Spanish Civil War, the outbreak of the Second Sino-Japanese War in 1937, and Germany's annexations of Austria and the Sudetenland. World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland, after which the United Kingdom and France declared war on Germany. Poland was also invaded by the Soviet Union in mid-September, and was partitioned between the two states under the Molotov–Ribbentrop Pact. In 1940, the Soviet Union annexed the Baltic states and parts of Finland and Romania, while Germany conquered Norway, Denmark, Belgium, Luxembourg, and the Netherlands.
Why it matters
After the fall of France in June 1940, the war continued, mainly between Germany, now assisted by Fascist Italy, and the British Empire and British Commonwealth, with fighting in the Balkans, Mediterranean, Middle East, East Africa, the aerial Battle of Britain, the Blitz, and the naval Battle of the Atlantic. By mid-1941, Yugoslavia and Greece had also been defeated by Axis countries. In June 1941, Germany invaded the Soviet Union, opening the Eastern Front. In December 1941, Japan attacked American and British territories in Asia and the Pacific, including Pearl Harbor in Hawaii, leading the United States to enter the war against the Axis. Japan conquered much of coastal China and Southeast Asia, but its advances in the Pacific were halted in June 1942 at the Battle of Midway.
Related on thisDay
Cite this page
“World War II.” thisDay, thisday.info/history/world-war-ii/. Accessed 19 Oct. 2026.
World War II. (n.d.). thisDay. Retrieved October 19, 2026, from https://thisday.info/history/world-war-ii/
“World War II.” thisDay. Accessed October 19, 2026. https://thisday.info/history/world-war-ii/.