World War II

Conflict

World War II (the Second World War) (as of 2026-09-05)^[1]

Dates

1 September 1939 – 2 September 1945 (as of 2026-09-05)^[1]

Belligerents

Allies and Axis powers (as of 2026-09-05)^[1]

Estimated deaths

60 to 75 million people, most of them civilians (as of 2026-09-05)^[1]

Outbreak

Germany invaded Poland on 1 September 1939 (as of 2026-09-05)^[1][3]

End in Europe

Germany surrendered unconditionally in May 1945 (8 May per Wikipedia contributors; 7 May in the west and 9 May in the east per the United States Holocaust Memorial Museum) (as of 2026-09-05)^[1][3]

End in the Pacific

Japan announced surrender on 15 August 1945 and signed the surrender document on 2 September 1945 (as of 2026-09-05)^[1]

Major international outcome

Creation of the United Nations, formally established on 24 October 1945 (as of 2026-09-05)^[4]

Overview

World War II was a worldwide conflict waged between the Allies and the Axis powers from 1 September 1939 to 2 September 1945.^[1] Virtually every nation took part in the war.^[1] According to Imperial War Museums, the 1939–1945 conflict was the most destructive in history.^[2]

The war's origins included lingering resentments from World War I, the ascendancy of fascism in Europe, and growing militarism in Japan.^[1] Key events preceding the war comprised Japan's 1931 invasion of Manchuria, the Spanish Civil War, the beginning of the Second Sino-Japanese War in 1937, and Germany's annexation of Austria and the Sudetenland.^[1]

Course of the war

Outbreak and expansion of the Axis, 1939–1941

The conflict is widely seen as having started on 1 September 1939, with Nazi Germany's invasion of Poland under Adolf Hitler.^[1] Lingering international tensions and the aggressive expansion pursued by Fascist Italy and Nazi Germany reached their peak in that invasion.^[2] Britain and France declared war on Germany following the invasion of Poland.^[1][2]

Britain entered the war on 3 September 1939.^[2] The Soviet Union invaded Poland in mid-September 1939, and under the terms of the Molotov–Ribbentrop Pact the country was partitioned between Germany and the Soviet Union.^[1]

In 1940 Germany conquered Norway, Denmark, Belgium, Luxembourg, and the Netherlands.^[1] In May 1940 Germany initiated Blitzkrieg tactics against Western Europe, assaulting France and the Low Countries.^[2] The German assault in France forced the British Expeditionary Force, together with French and Belgian troops, back toward the French port of Dunkirk.^[2] Germany captured France in June 1940.^[1]

In 1940 the Soviet Union additionally annexed parts of Finland and Romania.^[1] After the fall of France, fighting continued largely between Germany—supported by Fascist Italy—and the British Empire and Commonwealth, across the Balkans, the Mediterranean, the Middle East, East Africa, the Battle of Britain, the Blitz, and the Battle of the Atlantic.^[1] Running from 10 July to 31 October 1940 over southern England, the Battle of Britain was a major air campaign that proved a decisive confrontation.^[2]

From September 1940, Hitler directed the Luftwaffe to begin bombing British cities, and over the next nine months the Blitz killed more than 43,500 civilians.^[2] By mid-1941 Axis powers had conquered Yugoslavia and Greece.^[1] Germany overran and occupied Poland (September 1939), Denmark (April 1940), Norway (April 1940), Belgium (May 1940), the Netherlands (May 1940), Luxembourg (May 1940), France (May 1940), Yugoslavia (April 1941), and Greece (April 1941).^[3]

0:00 Introduction: WWII Opening segment of the CrashCourse overview of the war.

0:36 When did WWII start? Segment from the same video discussing the outbreak of the conflict.

Turning points, 1941–1943

On 22 June 1941, German forces invaded the Soviet Union, opening the Eastern Front.^[1][3] In December 1941 Japan attacked American and British territories across Asia and the Pacific, among them Pearl Harbor in Hawaii, bringing the United States into the war against the Axis.^[1] Japan's December 1941 offensive also struck British holdings in Hong Kong, Malaya, Singapore, and Burma.^[2]

On 7 December 1941, Japan launched a surprise aerial attack against the American naval installation at Pearl Harbor, Hawaii.^[2] On 15 February 1942, Lieutenant General Arthur Percival capitulated with 85,000 troops to a Japanese force of 35,000 at Singapore—the largest surrender ever recorded in British military history.^[2] At the Battle of Midway in June 1942, Japan's expansion across the Pacific was halted.^[1] By 1942 Nazi Germany had attained the peak of its territorial growth.^[3]

Early in 1943, Axis troops suffered defeats in North Africa and at Stalingrad within Soviet territory.^[1] An Allied landing in Italy during July 1943 brought down the country's fascist government.^[1] Allied advances across the Pacific and within Soviet territory pushed Axis forces back on every front during 1943–1944.^[1]

3:47 1941 Was Kind of a Bad Year Segment from the CrashCourse overview covering the events of 1941.

5:29 The Battle of Stalingrad Segment from the same video covering the Battle of Stalingrad.

1:52 The European Theater of World War II Segment from the CrashCourse overview covering the European theatre.

Allied victory, 1944–1945

On 6 June 1944, Allied troops initiated Operation Overlord, beginning the liberation of north-west Europe from German control.^[2] During 1944 the Western Allies landed in France at Normandy, establishing another front.^[1] Rome's liberation came in June 1944.^[3] On 16 December 1944 Germany mounted a large-scale assault on Allied troops in the Ardennes area of Belgium and Luxembourg, producing the 'bulge' that named the Battle of the Bulge.^[2] The Allied Powers started the methodical bombing of Germany in 1942, a campaign that ran until Germany's capitulation in 1945.^[3]

On 30 April 1945, Adolf Hitler committed suicide.^[3] Germany's unconditional surrender ended World War II in Europe in May 1945: Wikipedia contributors date it to 8 May 1945,^[1] while the United States Holocaust Memorial Museum records that German forces surrendered unconditionally to the Western Allies at Reims on 7 May and to the Soviets in Berlin on 9 May 1945.^[3]

On 6 and 9 August 1945, the United States detonated atomic bombs over Hiroshima and Nagasaki.^[1] The Soviet Union subsequently launched an invasion of Japanese-held Manchuria following the atomic bombings.^[1] Japan announced its unconditional surrender on 15 August 1945 and formally executed an instrument of surrender on 2 September 1945.^[1]

The Holocaust

Nazi Germany and its accomplices carried out the Holocaust, a state-directed, methodical persecution and extermination of European Jewry, between 1933 and 1945.^[3] Driven by the aim of building a German 'master race', the Nazis persecuted and killed Jews along with many others.^[3]

Adolf Hitler and the Nazi leadership envisioned an expansive new empire of 'living space' (Lebensraum) in eastern Europe for Germans, to be achieved through the displacement of existing populations.^[3] From 1941 to 1944, Nazi German authorities deported millions of Jews from Germany, occupied territories, and Axis-allied states to ghettos and killing centres.^[3] Six million Jews died in the Holocaust; Roma, the disabled, and Poles were likewise targeted for extermination, and millions of others—including homosexuals, Jehovah's Witnesses, Soviet prisoners of war, and political dissidents—suffered severe Nazi persecution.^[3]

Consequences

With an estimated 60 to 75 million deaths—most of them civilians—World War II stands as the deadliest conflict in recorded history.^[1] Large numbers perished from massacres, starvation, disease, and genocides such as the Holocaust.^[1]

In the aftermath of the Allied triumph, Germany, Austria, Japan, and Korea came under occupation, and German and Japanese leaders faced trials for war crimes.^[1] Delegates from 50 nations met in San Francisco between 25 April and 26 June 1945 to prepare and sign the UN Charter.^[4] The United Nations was founded to encourage international collaboration and head off future wars.^[1]

The United Nations was formally established on 24 October 1945, following ratification of its Charter by China, France, the Soviet Union, the United Kingdom, the United States, and the majority of the remaining signatories.^[4] China, France, the Soviet Union, the United Kingdom, and the United States were named the permanent members of the UN Security Council.^[1]

Following the war, the United States and the Soviet Union arose as competing superpowers, laying the groundwork for the Cold War.^[1] As Europe lay in ruins, its former dominant powers lost their standing, which set off decolonisation across Africa and Asia.^[1] The conflict reshaped global political, economic, and social institutions and laid the groundwork for international relations throughout the remainder of the twentieth century and into the twenty-first.^[1]

Educational videos

0:00 WW2 - OverSimplified (Part 1) Recording by OverSimplified, from the start of the video.

Timeline

1. 1931-09-18 According to Wikipedia contributors, Japan invades Manchuria, one of the events preceding the war.^[1]
2. 1937-07-07 According to Wikipedia contributors, Outbreak of the Second Sino-Japanese War, another precursor to the global conflict.^[1]
3. 1939-09-01 Germany invades Poland, the generally accepted start of World War II.^[1][2][3]
4. 1939-09-03 Britain enters the war against Germany.^[2]
5. 1940-07-10 Start of the Battle of Britain air campaign, fought over southern England until 31 October 1940.^[2]
6. 1941-06-22 Germany invades the Soviet Union, opening the Eastern Front.^[1][3]
7. 1941-12-07 Japan attacks Pearl Harbor, drawing the United States into the war.^[1][2]
8. 1942-02-15 Fall of Singapore and the largest surrender in British history.^[2]
9. 1944-06-06 Allied invasion of Normandy (Operation Overlord).^[1][2]
10. 1945-05-08 Germany's unconditional surrender ends the war in Europe (8 May per Wikipedia contributors; 7 May in the west and 9 May in the east per the United States Holocaust Memorial Museum).^[1][3]
11. 1945-08-15 Japan announces its unconditional surrender.^[1]
12. 1945-09-02 Japan signs the surrender document, formally ending World War II.^[1]
13. 1945-10-24 The United Nations officially begins after ratification of its Charter.^[4]