Curriculum fit: KS3 and GCSE History (Britain and the world, 1901 to the present in the National Curriculum); US middle and high school history; AP World and US History. Exam boards vary.
On this page
What Is It?
The Second World War was the largest conflict in history. It began in Europe in 1939 and became a global war involving most countries. It ended in 1945.
It was fought between the Allies, including Britain, the Soviet Union, the United States and China, and the Axis powers, mainly Germany, Italy and Japan.
Key Formulas and Ideas
- Causes: resentment of the Treaty of Versailles, the Great Depression, the rise of dictators and the policy of appeasement.
- Start in Europe: Germany invaded Poland on 1 September 1939, and Britain and France declared war on 3 September.
- Key events: Dunkirk (1940), Battle of Britain (1940), Operation Barbarossa (1941), Pearl Harbor (7 December 1941), D-Day (6 June 1944).
- End: VE Day 8 May 1945. Japan announced surrender on 15 August 1945 and signed on 2 September 1945.
Worked Examples
Why Did War Break Out?
Explain why Britain and France declared war in 1939.
- Germany invaded Poland on 1 September 1939.
- Britain and France had promised to support Poland.
- Germany did not withdraw, so they declared war on 3 September.
✓ Answer They had guaranteed Poland's independence
A Turning Point
Why was the entry of the United States important?
- Japan attacked Pearl Harbor in December 1941, and the US entered the war.
- The US added huge industrial and military resources to the Allies.
✓ Answer It greatly increased Allied strength
The Holocaust
What was the Holocaust?
- The Nazi regime persecuted Jews and other groups.
- About six million Jews were murdered in an organised genocide.
✓ Answer The Nazi genocide of European Jews and persecution of other groups
Common Mistakes to Avoid
- Confusing the dates of VE Day and VJ Day.
- Treating the war as only a European conflict.
- Listing events without explaining their significance.
- Mixing up Axis and Allied powers.
Practice Questions
Frequently Asked Questions
Why did Britain and France declare war?
They had guaranteed Poland's independence and demanded Germany withdraw after the invasion.
What was appeasement?
The policy of giving in to Hitler's demands to avoid war, as in the Munich Agreement of 1938.
Keep Going With These Guides
The Weimar Republic and How Hitler Rose to Power
See why the Weimar Republic struggled, how the Great Depression helped the Nazis and how Hitler gained power in 1933.
GCSEA-LevelHigh SchoolAPThe Cold War: Causes, Key Events and How It Ended
Understand the rivalry between the US and the Soviet Union from 1945 to 1991, with key events such as the Berlin Wall and the Cuban Missile Crisis.
GCSEA-LevelHigh SchoolAPCauses of World War One: MAIN Causes and the Trigger
Learn the long-term causes of the First World War (militarism, alliances, imperialism, nationalism) and how the 1914 assassination set it off.
GCSEA-LevelHigh SchoolAPSources and Review
Reviewed by StudyMorrow editorial review on 5 Nov 2026.