World War-1 (1914–1918) – Complete UPSC Prelims + Mains Revision Notes 

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1. Background of World War-1

A. Europe Before 1914

• Europe was dominated by Great Powers competing for colonies, trade routes, and military strength.

• After the unification of Germany in 1871, it became Europe’s fastest-growing industrial and military power.

• Old empires were weakening:

  • Ottoman Empire – called “Sick Man of Europe”

  • Austro‑Hungarian Empire – ethnic tensions rising

 The Balkan region became unstable and was called “Powder Keg of Europe.”

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B. Major Causes – Remember M.A.I.N.

1. Militarism

• Countries built massive armies and navies.

• Arms race between Germany and United Kingdom.

• Compulsory military service common.

 Europe was ready for war even before 1914.

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2. Alliance System

• Countries formed military alliances for protection.

Triple Entente

• United Kingdom

• France

• Russia

Triple Alliance

• Germany

• Austria‑Hungary

• Italy

Alliances turned a small conflict into a world war.

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3. Imperialism

• European powers competed for colonies in Africa & Asia.

• Example → Moroccan Crises between Germany & France.

 Rivalry increased hostility.

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4. Nationalism

• Balkan nationalism led by Serbia.

• Slavic people wanted independence from Austria-Hungary.

• France wanted revenge for losing Alsace-Lorraine to Germany.

 National pride made compromise impossible.

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2. Immediate Cause – Sarajevo Incident

• Date → 28 June 1914

• Place → Sarajevo

• Victim → Archduke Franz Ferdinand

• Assassin → Gavrilo Princip (Black Hand group)

Chain Reaction

• Austria-Hungary blamed Serbia.

• Issued ultimatum.

• Declared war on 28 July 1914.

• Alliances activated → World War began.

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3. Countries in the War

Central Powers

• Germany

• Austria-Hungary

• Ottoman Empire

• Bulgaria

Allied Powers

• Britain, France, Russia

• Serbia, Belgium

• Italy (1915)

• USA (1917)

• Japan, Greece, Romania, Portugal

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4. Important Military Plans

Schlieffen Plan

• Germany planned to defeat France quickly via Belgium.

• Then fight Russia.

 Failed at First Battle of the Marne (1914).

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5. Major Events & Battles (Chronological)

1914

• Germany invaded Belgium → Britain joined war.

• Battle of Marne → German advance stopped.

• Trench warfare began.

1915

• Gallipoli Campaign – Allied defeat.

• Poison gas first used at Second Battle of Ypres.

• RMS Lusitania sinking angered USA.

1916

• Battle of Verdun – Massive casualties.

• Battle of the Somme – First tanks.

• Battle of Jutland – Biggest naval battle.

1917

• Russian Revolution → Russia exited war.

• Zimmermann Telegram → USA entered war.

1918

• Germany Spring Offensive failed.

• Allies launched Hundred Days Offensive.

• Armistice → 11 November 1918.

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6. Important Military Features

• Trench Warfare – Defensive stalemate.

• Machine Guns & Artillery – Huge casualties.

• Tanks – Introduced by Britain.

• Aircraft – Reconnaissance & bombing.

• U-boats – German submarines.

• Chemical Weapons – Chlorine & Mustard gas.

War became industrial and deadly.

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7. USA Entry into War (1917)

Reasons:

• German unrestricted submarine warfare.

• Lusitania sinking.

• Zimmermann Telegram.

• Economic ties with Allies.

Effect:

• Fresh troops & resources.

• Boosted Allied morale.

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8. Russian Exit

• Bolshevik Revolution led by Vladimir Lenin.

• Treaty of Brest‑Litovsk (1918).

• Russia lost territory but exited war.

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9. End of War

Reasons for German defeat:

• USA entry.

• Naval blockade by Britain.

• Failed Spring Offensive.

• Internal revolutions in Germany.

• Collapse of Austria-Hungary & Ottoman Empire.

 Armistice signed on 11 Nov 1918.

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10. Treaty of Versailles (1919)

Main Terms:

• Germany accepted war guilt.

• Paid reparations.

• Army limited to 100,000.

• Lost colonies.

League of Nations created.

New countries formed:

• Poland

• Czechoslovakia

• Yugoslavia

• Finland

Treaty created resentment → Rise of Hitler → WW-2.

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11. Impact of World War-1

Political

• Collapse of German, Ottoman, Austro-Hungarian & Russian empires.

Economic

• Europe devastated.

• USA became economic leader.

Social

• Women entered workforce.

• “Lost Generation.”

Global Impact

• New borders created instability.

• Led to World War-2.

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12. Important Personalities

• Kaiser Wilhelm II – Germany

• Tsar Nicholas II – Russia

• Woodrow Wilson – USA

• Ferdinand Foch – Allied commander

• Paul von Hindenburg & Erich Ludendorff – German generals

• Mustafa Kemal Atatürk – Gallipoli hero

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 Important Facts for UPSC Prelims

• Duration → 1914–1918

• USA joined → 1917

• Treaty → 1919

• Armistice → 11 Nov 1918

• First tanks → Somme

• First gas attack → Ypres

• Casualties → ~10 million soldiers

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14. Memory Tricks

• Causes → MAIN

• Alliances → TE vs TA

• War End → ATG Collapse
  (Austria-Hungary, Turkey, Germany)

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 Previous UPSC Questions on World War-1

Example Prelims Questions

1. Which country left WW-1 after the Russian Revolution?
   Answer → Russia

2. Treaty of Versailles mainly punished which country?
   Answer → Germany

3. Gallipoli Campaign was fought against which empire?
   Answer → Ottoman Empire

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 Mains Answer Writing Tips

 Structure Answer like:

1. Causes

2. Course of War

3. Treaty

4. Impact

Add diagrams/maps for better marks.