World War II was a global war from 1939 to 1945 in which the Axis powers (mainly Nazi Germany, Italy, and Japan) fought the Allied powers (including Britain, the Soviet Union, the United States, China, and others), causing tens of millions of deaths and reshaping the modern world.

Quick Scoop: What happened in World War 2?

World War 2 began when Germany invaded Poland on 1 September 1939, prompting Britain and France to declare war on Germany two days later. Over the next six years, fighting spread across Europe, Africa, Asia, and the world’s oceans, turning it into the deadliest conflict in human history.

Main causes and build‑up

  • The harsh peace terms and economic chaos after World War I, especially in Germany, created resentment and instability that extremist movements could exploit.
  • Adolf Hitler’s Nazi regime in Germany and fascist dictatorships in Italy and militarist Japan pursued aggressive expansion, rejecting the post‑WWI order.
  • Germany reoccupied the Rhineland, annexed Austria (the Anschluss), and dismantled Czechoslovakia while Britain and France mostly avoided war, hoping appeasement would preserve peace.
  • In August 1939, Germany and the Soviet Union signed a non‑aggression pact that secretly divided Eastern Europe into spheres of influence, clearing the way for the invasion of Poland.

How the war started and spread (1939–1941)

  • September 1939: Germany invaded Poland from the west; shortly after, the Soviet Union invaded from the east, and Poland was defeated and partitioned.
  • 1940: Germany used blitzkrieg (“lightning war”) to rapidly conquer Denmark, Norway, the Netherlands, Belgium, and France; France fell in June 1940, and Britain stood alone in Western Europe.
  • 1940: The Battle of Britain saw massive air attacks on the UK, but the Royal Air Force stopped Germany from gaining air superiority, preventing an invasion.
  • In the Mediterranean and North Africa, Germany and Italy fought British and Commonwealth forces for control of vital sea routes and oil‑rich regions.
  • 22 June 1941: Germany launched Operation Barbarossa, a massive invasion of the Soviet Union aimed at destroying it as a power and seizing land and resources.
  • In Asia, Japan had already invaded large parts of China in the 1930s and sought to dominate East and Southeast Asia.

The war becomes truly global

  • 7 December 1941: Japan attacked the U.S. Pacific fleet at Pearl Harbor, triggering U.S. entry into the war; Japan also struck British and Dutch colonial possessions across Asia.
  • Following Pearl Harbor, Germany and Italy declared war on the United States, formally tying the European and Pacific wars into a single global conflict.
  • The main alliances solidified: Axis (Germany, Italy, Japan) versus Allies (Britain and Commonwealth, Soviet Union, United States, China, and many other states and governments‑in‑exile).

Turning points (1942–1943)

  • In North Africa, Axis forces were defeated at El Alamein and then driven out by late 1942–1943, removing the Axis threat to the Suez Canal and Middle Eastern oil.
  • On the Eastern Front, the Soviet victory at Stalingrad (1942–1943) and later at Kursk in 1943 halted and then reversed German advances, putting Germany on the defensive.
  • In the Pacific, U.S. victories at Midway (1942) and Guadalcanal shifted the balance, crippling Japanese naval power and enabling Allied “island‑hopping” toward Japan.

How the war ended in Europe (1944–1945)

  • 6 June 1944: The Western Allies landed in Normandy (D‑Day), opening a second front in Western Europe and beginning the liberation of France and Western Europe.
  • As Allied forces advanced from the west, the Soviet Red Army pushed from the east through Eastern Europe and into Germany itself.
  • Germany’s last major offensive in the west, the Battle of the Bulge in winter 1944–1945, failed, exhausting its remaining reserves.
  • In April 1945, Soviet forces captured Berlin; Adolf Hitler committed suicide on 30 April, and Germany surrendered unconditionally on 8 May 1945 (V‑E Day).

How the war ended in Asia and the Pacific

  • In 1944–1945, the Allies recaptured the Philippines and seized key islands such as Iwo Jima and Okinawa, bringing bombers within range of the Japanese home islands.
  • U.S. air raids devastated Japanese cities, and Japan’s navy and air power were largely destroyed, but its leadership refused to surrender.
  • 6 and 9 August 1945: The United States dropped atomic bombs on Hiroshima and Nagasaki, killing tens of thousands instantly and many more over time.
  • The Soviet Union declared war on Japan and invaded Japanese‑held Manchuria in August 1945, further undermining Japan’s position.
  • Japan accepted unconditional surrender on 15 August and signed the formal surrender on 2 September 1945, ending World War 2.

Atrocities, the Holocaust, and civilian suffering

  • World War 2 was marked by systematic atrocities, including genocides, massacres, forced labor, and mass starvation.
  • The Holocaust was Nazi Germany’s attempt to annihilate European Jews; around six million Jews were murdered, along with millions of other victims such as Roma, disabled people, political prisoners, and others.
  • In Asia, Japanese forces committed large‑scale crimes such as the Nanjing Massacre and human experimentation (for example, Unit 731), and harsh occupation policies caused vast civilian suffering.
  • Strategic bombing by both Axis and Allies destroyed many cities and killed large numbers of civilians in Europe and Japan.

Consequences and what changed after

  • World War 2 is often considered the deadliest conflict in history, causing the deaths of over 60 million people, including combatants and civilians.
  • Germany, Austria, Japan, and Korea were occupied after the war; Germany was divided, and many German and Japanese leaders were tried for war crimes in international tribunals.
  • The United States and the Soviet Union emerged as rival superpowers, and their ideological conflict soon evolved into the Cold War.
  • The United Nations was created in 1945 to help prevent future large‑scale wars and promote international cooperation.
  • Decolonization accelerated after the war, with many Asian and African nations eventually gaining independence over the following decades.

Mini timeline of key events (HTML table)

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Year Event
1939 Germany invades Poland; Britain and France declare war.
1940 Fall of France; Battle of Britain.
1941 Germany invades the Soviet Union; Japan attacks Pearl Harbor; U.S. enters the war.
1942–1943 Turning points at Stalingrad, El Alamein, Midway, and Guadalcanal.
1944 D‑Day landings in Normandy; liberation of much of Western Europe.
1945 Germany surrenders in May; atomic bombs on Hiroshima and Nagasaki; Japan surrenders in September.

Different viewpoints and ongoing discussion

  • Military historians emphasize strategy and technology (blitzkrieg, air power, tanks, submarines, and nuclear weapons) to explain why battles unfolded as they did.
  • Social and cultural historians focus on everyday life under occupation, resistance movements, and how societies coped with bombing, rationing, and loss.
  • Moral debates continue over actions like strategic bombing and the atomic bombs, with some arguing they shortened the war and others stressing the massive civilian toll.
  • Online forums and modern discussions often link World War 2 to current events—such as rising nationalism, debates about war crimes, and the risk of great‑power conflict—showing how “what happened in World War 2” still feels relevant today.

“World War 2 isn’t just old history; it’s a warning sign about how economic crisis, extremist politics, and unchecked aggression can spiral into catastrophe.”

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.