World Wars & their aftermath

The First World War (1914–1918)

The Great War erupted on 28 July 1914 when Austria-Hungary declared war on Serbia, three weeks after the assassination of Archduke Franz Ferdinand at Sarajevo (28 June 1914). The proximate trigger masked deeper structural causes that UPSC repeatedly tests: the alliance system (the Triple Alliance of 1882 binding Germany, Austria-Hungary and Italy against the Triple Entente of 1907 linking Britain, France and Russia); aggressive nationalism in the Balkans (the 'powder keg of Europe'); militarism and the naval arms race symbolised by Britain's HMS Dreadnought (1906); and imperial rivalry over colonies and markets. Germany's Schlieffen Plan—a two-front war strategy—drew Britain in via the violation of Belgian neutrality, guaranteed by the Treaty of London (1839).

The war became a war of attrition: the Western Front froze into trench stalemate after the First Battle of the Marne (1914), with catastrophic losses at Verdun and the Somme (1916). The United States entered in April 1917 following unrestricted submarine warfare and the Zimmermann Telegram. Russia exited after the Bolshevik Revolution (November 1917) and the Treaty of Brest-Litovsk (March 1918).

The Second World War (1939–1945)

The Second World War began on 1 September 1939 with Germany's invasion of Poland, prompting Anglo-French declarations of war. Its roots lay substantially in the punitive Treaty of Versailles (1919)—the 'war guilt' clause (Article 231), reparations and territorial losses that fed German revanchism. The Great Depression (from 1929) discredited liberal democracy and fuelled fascism: Mussolini's March on Rome (1922) and Hitler's appointment as Chancellor (30 January 1933). Appeasement culminated in the Munich Agreement (September 1938) ceding the Sudetenland; the Nazi-Soviet Pact (August 1939) cleared the path to war.

Key turning points UPSC expects candidates to marshal: the Battle of Britain (1940), Operation Barbarossa (June 1941) opening the Eastern Front, the Japanese attack on Pearl Harbor (7 December 1941) bringing in the US, the Battle of Stalingrad (1942–43), D-Day (6 June 1944), and the atomic bombings of Hiroshima and Nagasaki (6 and 9 August 1945). Germany surrendered on 8 May 1945; Japan on 2 September 1945.

The war's human and moral catastrophe—the Holocaust, the genocide of roughly six million Jews—reshaped international law and led directly to the Genocide Convention (1948) and the Universal Declaration of Human Rights (1948). For Asia and Africa, the wars accelerated decolonization: the exhaustion of European imperial powers, the demonstration effect of Japanese victories over Western forces (the fall of Singapore, 1942), and wartime promises such as the Atlantic Charter (1941) invoking self-determination all eroded the legitimacy of empire.

The Peace Settlements

The Paris Peace Conference (1919) produced the Treaty of Versailles (28 June 1919), dictated by the 'Big Three'—Woodrow Wilson (US), David Lloyd George (Britain) and Georges Clemenceau (France). Wilson's Fourteen Points (January 1918) advanced open diplomacy, freedom of the seas and national self-determination, but the final treaty was punitive: Germany lost Alsace-Lorraine, accepted demilitarisation of the Rhineland, surrendered colonies as League 'mandates', and bore reparations fixed in 1921 at 132 billion gold marks. Companion treaties—Saint-Germain (Austria), Trianon (Hungary), Neuilly (Bulgaria) and Sèvres (Ottoman Empire, later revised by Lausanne, 1923)—dismantled four empires (German, Austro-Hungarian, Ottoman, Russian) and redrew the map of Europe and West Asia, sowing future grievances.

From League to United Nations

The League of Nations, established under the Covenant embedded in the Versailles treaty (effective January 1920), was the first general international organisation for collective security. It failed structurally: the United States never joined (the US Senate rejected ratification in 1919–20); it lacked an armed force; decisions required unanimity; and it could not check aggression—Japan's invasion of Manchuria (1931), Italy's conquest of Abyssinia (1935–36) and German remilitarisation each exposed its impotence.

The United Nations, chartered at San Francisco on 26 June 1945 and effective 24 October 1945, corrected these defects. The Security Council vested enforcement power in five permanent members (the US, USSR, UK, France and China) wielding the veto under Article 27; Chapter VII authorised collective coercive action. Allied wartime diplomacy—the Atlantic Charter (1941), the Tehran (1943), Yalta (February 1945) and Potsdam (July–August 1945) conferences—shaped the post-war order, including the partition of Germany and the seeds of the Cold War.

Why this matters for the exam

In UPSC Mains GS-1, world history appears under 'history of the world... World Wars... redrawal of national boundaries, colonisation, decolonisation'. The World Wars are a high-yield zone because questions are typically analytical, not factual: PYQs have asked candidates to assess whether the Treaty of Versailles caused the Second World War, why the League of Nations failed, and how the World Wars accelerated decolonisation. The examiner rewards a thesis-driven structure—causes classified (alliances, militarism, nationalism, imperialism), turning points dated, and consequences traced into institutions (UN), ideologies (fascism, communism) and the global South's freedom movements. Retain the treaty names, the four collapsed empires, the Wilsonian Fourteen Points, and the Yalta–Potsdam sequence as deployable facts. Link world events to Indian history: the wars' fiscal drain on Britain and the 1947 transfer of power are connectable in synoptic answers.