World history: the world wars and the modern world (grade 10) · lesson

World War I

💡 Alliances turned a local crisis into a world war, and the harsh peace that followed planted seeds of the next war.

In 1914, Archduke Franz Ferdinand, heir to the throne of Austria-Hungary, was killed. Countries had promised to defend their allies, so one nation after another joined the fight. A regional crisis became a world war.

On the Western Front in France and Belgium, armies dug trenches. Machine guns and artillery made attacks across open ground very costly, so the front barely moved for years.

The Treaty of Versailles in 1919 blamed Germany for the war. Germany lost land and colonies and had to pay reparations. Many Germans resented the treaty, and later leaders used that anger to win support.

🧠 Let's work it out

Ask how a small event grew big.
Look for promises, like alliances, that pulled others in.
For a peace treaty, ask how the losing side would feel and what they might do years later.

What do you think comes next?

alliance: an agreement between nations to support each other
reparations: payments a defeated nation must make for war damages

🔗 Khan Academy: Global conflict · Khan Academy (free) ↗

The road to World War II

💡 Resentment, economic depression, and giving in to aggression helped lead the world back to war.

After World War I came the Treaty of Versailles (1919). Then the Great Depression began in 1929 and threw millions of Germans out of work. Anger and hardship helped Hitler's Nazi Party win support, and Hitler took power in 1933.

Germany began taking land. In 1938 at Munich, Britain and France let Germany take part of Czechoslovakia, hoping to avoid war. This policy is called appeasement. It failed. In 1939, Germany seized the rest of Czechoslovakia and invaded Poland, starting World War II in Europe. The war ended in 1945, and the United Nations was founded that year.

🧠 Let's work it out

To test a policy like appeasement, compare what it promised with what happened next.
Munich promised peace.
Within a year, Germany took more land and invaded Poland.

What do you think comes next?

appeasement: giving in to an aggressor's demands to avoid war
Great Depression: the worldwide economic collapse that began in 1929

The Cold War

💡 The US and the Soviet Union competed for decades without fighting each other directly, until the Soviet system weakened from within.

From about 1947 to 1991, the United States and the Soviet Union competed through an arms race, alliances, and wars fought by others. It was called 'cold' because the two never fought each other in a full-scale war.

The closest call came in 1962. The Soviet Union placed nuclear missiles in Cuba, about 90 miles from Florida. The standoff brought the world close to nuclear war until the Soviets removed the missiles.

Communist East Germany built the Berlin Wall in 1961 to stop people from leaving for the West. In 1989, East German leaders suddenly allowed free travel and guards opened the gates, showing Soviet-backed governments were losing control. A struggling Soviet economy and Gorbachev's reforms, which allowed more openness, helped end the Cold War. The Soviet Union broke apart in 1991.

🧠 Let's work it out

Ask what a symbol was built to do.
The Berlin Wall was built to keep people in.

What do you think comes next?

Cold War: the long rivalry between the US and the Soviet Union, about 1947 to 1991
arms race: a contest to build more and stronger weapons

The UN and the end of empires

💡 After 1945, nations built the UN to keep the peace, and a weakened Europe lost most of its colonies.

The United Nations was founded in 1945 as World War II ended. Its goals were to keep peace and security among nations and to promote cooperation on problems like human rights. Member nations kept their own governments.

World War II left European powers worn out and in debt. At the same time, independence movements had grown strong, like the one led by Gandhi in India. Over the next few decades, most colonies in Asia and Africa became independent through many different struggles.

🧠 Let's work it out

Look at both sides of a change.
What made the old power weaker, and what made the challengers stronger?

What do you think comes next?

decolonization: colonies gaining independence
United Nations: an organization of nations founded in 1945 to keep peace