World War 2 — Causes, Events & Summary
Key Points At A Glance
- World War 2 lasted from 1939 to 1945 and involved over 30 countries.
- It was fought between the Allied Powers and the Axis Powers.
- A major cause was the harsh Treaty of Versailles after World War 1.
- The immediate cause was Germany's invasion of Poland in 1939.
- The war ended in 1945 after Germany surrendered and Japan was bombed.
- The United Nations was formed in 1945 to prevent future world wars.
World War 2 was the largest and deadliest conflict in human history, involving more than 30 countries and reshaping the entire world. It is a key topic in history exams — but it is also a story of why peace matters. These notes give you a clear, simple summary of what happened and why.
What Was World War 2?
World War 2 was a global war that lasted from 1939 to 1945. It was fought between two main groups of countries:
- The Allied Powers — including Britain, France, the Soviet Union, the United States and others.
- The Axis Powers — mainly Germany, Italy and Japan.
Main Causes of World War 2
Wars rarely have a single cause. World War 2 grew out of several problems, many of them left over from World War 1:
- The Treaty of Versailles — the harsh treaty after World War 1 left Germany angry and economically weak.
- Rise of dictators — leaders like Adolf Hitler in Germany gained power by promising to restore national pride.
- Expansion and aggression — Germany, Italy and Japan began invading and taking over other territories.
- Failure of the League of Nations — the world body meant to keep peace was too weak to stop aggression.
How the War Spread
After the invasion of Poland, the war quickly expanded:
- Germany rapidly conquered much of Europe using fast "blitzkrieg" (lightning war) tactics.
- The war spread to North Africa and Asia.
- In 1941, two events widened the conflict: Germany attacked the Soviet Union, and Japan attacked the United States naval base at Pearl Harbor, bringing the USA into the war.
Key Turning Points
- Battle of Stalingrad — a huge defeat for Germany against the Soviet Union.
- D-Day (1944) — Allied forces landed in France and began freeing Europe.
- Surrender of Germany (May 1945) — ended the war in Europe.
- Atomic bombs on Japan (August 1945) — the USA dropped bombs on Hiroshima and Nagasaki, and Japan surrendered, ending the war.
Results and Effects of the War
World War 2 changed the world forever:
- Massive loss of life — an estimated 70–85 million people died.
- The United Nations was formed in 1945 to prevent future world wars.
- Two superpowers emerged — the United States and the Soviet Union — leading to the Cold War.
- The end of colonial empires began, as many countries moved towards independence.
Important Exam Questions
- Name the Allied and Axis powers.
- What was the immediate cause of World War 2?
- Why was the Treaty of Versailles a cause of the war?
- What international organisation was formed after the war, and why?
Quick Summary
- World War 2 lasted from 1939 to 1945.
- It was fought between the Allies and the Axis powers.
- The immediate cause was Germany's invasion of Poland.
- It led to the formation of the United Nations and the start of the Cold War.
History makes the most sense when you connect causes to effects, so try drawing a simple timeline of the events above. To memorise dates and names before your exam, use the techniques in How to Study Smart for Exams. Explore more Social Science notes and all our study notes any time.
Frequently Asked Questions
World War 2 lasted from 1939 to 1945. It began with Germany's invasion of Poland and ended with the surrender of Japan in 1945.
It was fought between the Allied Powers (Britain, France, the Soviet Union, the United States and others) and the Axis Powers (mainly Germany, Italy and Japan).
The immediate cause was Germany's invasion of Poland in September 1939, which led Britain and France to declare war on Germany.
Germany surrendered in May 1945, and after the United States dropped atomic bombs on Hiroshima and Nagasaki, Japan surrendered in August 1945, ending the war.
The war caused enormous loss of life, led to the formation of the United Nations, created two superpowers (the USA and USSR), and began the end of colonial empires.
Yolearning Teaching Team
Teachers, subject researchers and exam mentors who write clear, syllabus-friendly study notes the way they would actually explain a topic to a student sitting across the table.
