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IB Diploma History SL · Causes & Effects of 20th-Century Wars
Mini-Lesson

Causes & Effects of 20th-Century Wars

A Paper 2 comparative topic. You study the causes, practices and effects of two 20th-century wars from different regions.

This mini-lesson gives you the analytical framework — types of war, long- and short-term causes, and consequences — with verified examples from the World Wars, the Spanish Civil War and beyond. Collect ⭐ stars, then press Start.

Framework

How historians classify wars

The topic asks you to analyse types of war: total wars (whole societies mobilised, e.g. the World Wars), civil wars (e.g. the Spanish Civil War, 1936-1939), and guerrilla or limited wars. Comparing different types across regions is exactly what Paper 2 rewards.

Causes · long-term

Long-term causes

Long-term (underlying) causes build over years: the pre-1914 alliance system, militarism, imperial rivalry and nationalism before the First World War; unresolved grievances from the Treaty of Versailles (1919) before the Second.

Quick check

Comparative rule

?For this topic you compare:
Causes · short-term

Short-term causes and sparks

Short-term causes and triggers light the fuse. The assassination of Archduke Franz Ferdinand on 28 June 1914 triggered the First World War through the alliance system; the German invasion of Poland on 1 September 1939 triggered the Second.

Analytical habit: always separate underlying causes from the trigger — and argue about their relative weight.

Practices

How the wars were fought

"Practices" covers technology, strategy, the home front, propaganda and the treatment of civilians. Total war meant mobilising entire economies and populations, blurring the line between soldier and civilian and producing mass civilian casualties.

Quick check

Date the spark

?Archduke Franz Ferdinand was assassinated in:
Sort it

Cause or effect?

Sort each item as a long-term cause, a short-term trigger, or an effect of 20th-century wars.

⏳ Long-term cause

⚡ Short-term trigger

📉 Effect

Effects · political

Political and territorial effects

Wars redraw maps and topple regimes. The First World War ended four empires and produced the Treaty of Versailles (1919) and the League of Nations (1920). The Second World War led to the United Nations (founded 24 October 1945), the division of Europe and the onset of the Cold War.

Quick check

Date the treaty

?The Treaty of Versailles was signed in:
Match it

Match the concept

Tap an item on the left, then its match on the right.

Concept
Meaning
Effects · social & economic

Social and economic effects

Wars accelerate social change: shifts in the role of women, in technology, and in the economy (debt, reconstruction, inflation). They also leave demographic scars and shape memory and politics for generations.

Comparison

Comparing two wars

Choose two wars from different regions — for instance the Second World War (Europe/Asia) and the Chinese Civil War (which ended in Communist victory in 1949) or the Korean War (1950-1953). Compare their causes, character and consequences thematically.

Quick check

Define it

?"Total war" means a conflict in which:
Order it

Order these 20th-century war milestones

Tap the events in sequence, earliest first.

Essay craft

Building the comparative essay

Set out a clear line of argument, use a thematic structure (long-term vs short-term causes; political vs social effects), and support every claim with specific, dated evidence from two regions. Weigh factors against one another rather than listing them.

Recap

The big ideas to take away

Paper 2: compare two 20th-century wars from different regions across causes, practices, effects

Causes: separate long-term causes (alliances, nationalism) from the trigger

Practices: technology, home front, propaganda, total war

Effects: Versailles (1919), League (1920), UN (1945), the Cold War

Essay craft: thematic structure, dated evidence, weigh factors and judge

You can now analyse and compare the causes and effects of 20th-century wars. Press Finish to see your score.

🏆

Mini-lesson complete!

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You’ve worked through Causes & Effects of 20th-Century Wars for IB Diploma History SL. 🎉

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