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NotesHistoryTopic 16.3
Unit 16 · Paper 2 · Causes and effects of 20th-century wars · Topic 16.3

IB History — Effects of war

Topic 16.3 of IB History covers Effects of war, which is part of Unit 16: Paper 2 · Causes and effects of 20th-century wars. Students explore key concepts including Consequences of war: the framework, Effects of the First World War (1914–18), Effects of the Second World War (1939–45). A strong understanding of effects of war is essential for IB History exams and builds the foundation for connected topics across the syllabus.

Exam technique guidePractice questions

Key concepts in Effects of war

Key Idea: Wars do not stop when the fighting stops. This topic gives you a six-theme framework for the effects of any twentieth-century war — peacemaking, territorial, political, economic, social and human cost — and then applies it to the two world wars. WWI (ending 1918) broke four empires and left a fragile peace; WWII (ending 1945) killed tens of millions and split the world into two superpower blocs, starting the Cold War.

🧭 16.3.1 — A framework for the effects of war

When an essay asks about the effects of a war, the trap is to tell a story of what happened. Instead, sort the effects into clear themes and then weigh which mattered most.

Use the memory hook P-T-P-E-S-H. Split each effect into short-term (the years right after) and long-term (decades later), and notice they are linked — harsh reparations caused economic misery, which fed the rise of extreme parties.

  • Peacemaking — did the peace settlement and its international body last? Versailles + the League failed; the UN endured
  • Territorial — borders redrawn, new states born, the balance of power shifting between great powers
  • Political — regime change, revolution and new systems of government (e.g. the 1917 Russian Revolution)
  • Economic — cost, debt, reparations, economic dislocation and reconstruction
  • Social — everyday life changes, above all the changing role of women
  • Human cost — the dead and wounded, and the key split between military and civilian deaths

🌍 16.3.2 — Effects of the First World War

When the guns stopped on 11 November 1918, Europe was transformed. In 1919 the winners met in Paris, where the Big Three — Clemenceau (France, wanted Germany crushed), Wilson (USA, wanted a fair peace + a League) and Lloyd George (Britain, in the middle) — hammered out the Treaty of Versailles.

Versailles blamed Germany through Article 231 (the war-guilt clause), capped its army and imposed huge reparations (payments for war damage), which Germans resented as a humiliating Diktat (a dictated peace). The League of Nations was founded in 1920 but born weak: no USA, no army, and a unanimity rule that let one 'no' block everything.

  • Four empires fell — German, Austro-Hungarian, Russian and Ottoman — and new states appeared: Poland, Czechoslovakia, Yugoslavia (Wilson's idea of self-determination, a people's right to rule itself)
  • 1917 Russian Revolutions — two revolutions toppled the Tsar and brought Lenin's communist Bolsheviks to power, creating the world's first communist state
  • Economic — victors left in debt to the USA; Germany crippled by reparations; runaway inflation (worst in Germany, 1923)
  • Social — women's wartime work linked to the vote (Britain and Germany 1918, USA 1920)
  • Human cost — around 9–10 million soldiers dead (mostly military), plus the 1918–19 flu pandemic that killed tens of millions more

💥 16.3.3 — Effects of the Second World War

Unlike WWI, WWII had no single peace treaty. The Big Three planned the peace during the war — at Yalta (February 1945: Roosevelt, Stalin, Churchill) and Potsdam (July–August 1945, with Truman replacing the late Roosevelt and Attlee replacing Churchill). They agreed to split Germany into four occupation zones and founded the United Nations in 1945 — which fixed the League's flaws (the USA joined, no unanimity rule, and it could call on members' troops).

Germany was divided, and the USSR — whose Red Army had liberated Eastern Europe — installed communist governments there (Churchill's 1946 Iron Curtain). The USA and USSR emerged as rival superpowers with opposite systems, capitalism versus communism, beginning the Cold War. The war was the deadliest in history: an estimated 50–70 million dead, mostly civilians, including around six million Jews in the Holocaust.

  • Peacemaking — Yalta and Potsdam; the UN (1945) replaced the failed League
  • Territorial — Germany split into four zones, Berlin divided, Poland shifted west, USSR controlling Eastern Europe
  • Political — USA and USSR as superpowers; decolonisation accelerated (India 1947); communism spread (China 1949)
  • Economic — devastation met by the US Marshall Plan (1948, ~$13 billion) rebuilding Western Europe
  • Legacy — the Nuremberg Trials (1945–46) held leaders personally responsible, launching a new framework of international law and human rights

✍️ Exam-ready answers

IB-style questionExamine[15 marks]

Examine the effects of a twentieth-century war on the society in which it was fought. [15 marks]

🔒 Model answer plan

See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.

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IB-style questionTo what extent[15 marks]

To what extent were the effects of the First World War political rather than economic? [15 marks]

🔒 Model answer plan

See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.

Unlock free for 7 days →

🎯 One-glance recall

The six-theme framework P-T-P-E-S-H: Peacemaking, Territorial, Political, Economic, Social, Human cost. Sort effects into these, split short-term vs long-term, show how they link, then judge which mattered most.

WWI's effects (ended 1918) Versailles (1919) blamed Germany via Article 231 + reparations; weak League of Nations (1920). Four empires fell → Poland, Czechoslovakia, Yugoslavia. 1917 Russian Revolutions → first communist state. ~9–10m soldiers dead + 1918–19 flu.

WWII's effects (ended 1945) Yalta & Potsdam (1945) planned the peace; UN founded 1945. Germany divided; USSR took Eastern Europe (Iron Curtain) → Cold War. USA & USSR = superpowers; decolonisation; China communist 1949. 50–70m+ dead, mostly civilian (Holocaust); Marshall Plan 1948; Nuremberg 1945–46.

How Paper 2 tests this Essay-based, NOT source-based. Command terms (Examine, Evaluate, To what extent, Compare and contrast) need a thesis, themed arguments with dated evidence, and a weighed judgement — never a narrative list. If a question says 'wars', use examples from two different regions.

What you'll learn in Topic 16.3

  • 16.3.1 Consequences of war: the framework
  • 16.3.2 Effects of the First World War (1914–18)
  • 16.3.3 Effects of the Second World War (1939–45)
Suggested study order: Read the notes for each sub-topic below → test yourself with flashcards → attempt practice questions → review exam technique.

Study resources — 16.3 Effects of war

16.3.1

Consequences of war: the framework

Notes
16.3.2

Effects of the First World War (1914–18)

Notes
16.3.3

Effects of the Second World War (1939–45)

Notes

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Topic 16.3 Effects of war forms a core part of Unit 16: Paper 2 · Causes and effects of 20th-century wars in IB History. Mastering these concepts will strengthen your understanding of connected topics across the syllabus and prepare you for exam questions that require analysis, evaluation, and real-world application.

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