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World History · CDS

HC20 — World Wars & Interwar Period

📚 HC20 · World History – II  ·  Chapter 2 of 3 CDS Level ★ High Priority
📌 CDS Focus: WWI and WWII are regularly tested — specifically: the MAIN causes of WWI, Treaty of Versailles provisions, Hitler's rise, Pearl Harbour, D-Day, Holocaust, and the UN formation. The interwar Great Depression as a cause of WWII is a concept question. Matching leaders to countries (Hitler=Germany, Mussolini=Italy, Churchill=UK, Roosevelt=USA, Stalin=USSR) is a frequent MCQ format.
PART A — WORLD WAR I (1914–1918)

1. World War I — Causes & Key Events

1.1 Causes — MAIN Mnemonic Maximum PYQs

💡 MAIN — Causes of WWI: Militarism (arms race; naval rivalry Britain-Germany) → Alliances (Triple Alliance vs Triple Entente; interlocking treaties) → Imperialism (competition for colonies in Africa and Asia) → Nationalism (ethnic nationalism in Balkans; Austria-Hungary's instability). Immediate trigger: Assassination of Archduke Franz Ferdinand (heir to Austria-Hungary) at Sarajevo on 28 June 1914 by Gavrilo Princip (Serbian nationalist).

📌 Two Alliances — WWI

  • Triple Alliance (Central Powers): Germany + Austria-Hungary + Italy
  • Triple Entente (Allied Powers): Britain + France + Russia
  • Italy switched sides — joined Allies in 1915
  • USA joined Allies in 1917 (Zimmermann Telegram + Lusitania sinking)
  • Russia left after Revolution (Treaty of Brest-Litovsk 1918)

📌 Key Events — WWI

  • Assassination of Archduke Franz Ferdinand — 28 June 1914
  • War declared: Austria-Hungary vs Serbia → chain reaction through alliances
  • Battle of the Marne (1914) — Germans halted; trench warfare began
  • Battle of Verdun (1916) — longest battle; ~700,000 casualties
  • Battle of Somme (1916) — Britain's first use of tanks
  • USA entered: April 1917 (Zimmermann Telegram to Mexico)

1.2 Treaty of Versailles (1919) & League of Nations High Priority PYQ

AspectProvision / DetailCDS Note
War Guilt ClauseArticle 231 — Germany alone blamed for starting WWIHumiliated Germany; major cause of WWII
ReparationsGermany to pay £6.6 billion (later set); paid until 2010Crashed German economy; hyperinflation
Territorial lossesGermany lost Alsace-Lorraine (to France), Polish Corridor, all colonies; Austria-Hungary dissolvedGermany lost 13% of territory; 10% population
Military limitsArmy limited to 100,000; no air force; no submarines; Rhineland demilitarisedHitler later violated all these terms
League of NationsCreated by the Treaty; Woodrow Wilson's idea; USA never joined (Congress refused)USA not in League = major weakness; failed to prevent WWII
⚠ WWI Traps: (1) USA did NOT join the League of Nations — Wilson proposed it but US Congress rejected. (2) WWI ended: 11 November 1918 (11:11 AM — Armistice Day / Remembrance Day). (3) Treaty of Versailles was signed 28 June 1919 — exactly 5 years after Archduke's assassination. (4) Germany's primary enemy in WWI was France and Britain — NOT Russia (Russia left in 1917–18).
PART B — INTERWAR PERIOD & GREAT DEPRESSION

2. Interwar Period (1919–1939) & Great Depression

📈 Great Depression (1929–39)

  • Stock market crash: Wall Street Crash, 24 October 1929 ("Black Thursday")
  • US banks collapsed; credit dried up; factories closed; mass unemployment
  • Spread worldwide through trade and financial links
  • Germany hit hardest — already weak from war reparations; 30% unemployment
  • Roosevelt's New Deal (1933) — US government intervention to revive economy
  • Depression made populations desperate → attracted extremist politics (Fascism, Nazism)

📌 Rise of Fascism & Nazism

  • Benito Mussolini — founded Fascism in Italy (1919); became dictator (Il Duce); March on Rome 1922
  • Adolf Hitler — joined NSDAP (Nazi Party); failed Beer Hall Putsch (1923); wrote Mein Kampf in jail; became Chancellor 1933, then Führer
  • Hitler's ideology: racial superiority of Aryans; anti-Semitism; rejection of Versailles; pan-German nationalism
  • Aggressive expansion: Rhineland (1936), Austria (1938 — Anschluss), Sudetenland (1938)
PART C — WORLD WAR II (1939–1945)

3. World War II

3.1 Key Events — Timeline High Priority PYQ

EventDateSignificance
Poland Invasion1 September 1939Germany invades Poland; Britain and France declare war; WWII begins
Fall of FranceJune 1940Germany occupied France in 6 weeks; Dunkirk evacuation (340,000 troops rescued)
Battle of Britain1940German Luftwaffe vs RAF; Britain survived air attack; Churchill's leadership
Operation BarbarossaJune 1941Germany invaded USSR; Stalin joined Allies; Hitler's biggest strategic blunder
Pearl Harbor7 December 1941Japan bombed US naval base in Hawaii; USA joined the war
Battle of Stalingrad1942–43Germany defeated by USSR; turning point on Eastern Front; ~2 million casualties
D-Day (Operation Overlord)6 June 1944Allied invasion of Normandy, France; largest seaborne invasion in history; ~156,000 troops
V-E Day8 May 1945Germany surrendered; Victory in Europe Day
Hiroshima & Nagasaki6 & 9 Aug 1945US dropped atomic bombs; Japan surrendered 15 August 1945; V-J Day

3.2 Holocaust & War Crimes

The Holocaust: The systematic genocide of 6 million Jews (and millions of others — Roma, disabled, political prisoners, LGBTQ+) by Nazi Germany, primarily 1941–45. Key mechanism: concentration camps and extermination camps (Auschwitz, Treblinka, Sobibor). The Holocaust resulted in the Nuremberg Trials (1945–46) — the first international war crimes tribunal, setting the precedent for modern international law. The term "genocide" was coined to describe it (Raphael Lemkin, 1944).

3.3 Outcomes of WWII PYQ

🌎 United Nations Formation

  • UN Charter signed: 26 June 1945 at San Francisco
  • UN officially formed: 24 October 1945 (UN Day)
  • Replaced the failed League of Nations
  • 5 permanent members of Security Council: USA, USSR, UK, France, China (veto power)
  • First Secretary-General: Trygve Lie (Norway)

🌎 Cold War Begins

  • WWII ended with USA and USSR as two superpowers — ideologically opposed
  • Europe divided: Western (US sphere) vs Eastern (Soviet sphere)
  • Germany divided: West Germany (democratic) + East Germany (communist)
  • Iron Curtain — Churchill's phrase (1946) for Soviet-controlled Eastern Europe
  • Yalta Conference (1945) and Potsdam Conference (1945) — post-war division

⚡ HC20 Memory Chart — Fast Revision

⚔️ WWI — MAIN Causes
  • Militarism — arms race
  • Alliances — interlocking treaties
  • Imperialism — colonial rivalry
  • Nationalism — Balkan crisis
  • Trigger: Archduke shot — 28 June 1914
📜 Treaty of Versailles
  • Signed: 28 June 1919
  • War Guilt Clause — Germany blamed
  • Reparations — £6.6 billion
  • League of Nations — USA didn't join
  • WWI ended: 11 November 1918
📉 Interwar Period
  • Wall Street Crash: 24 Oct 1929
  • Great Depression: 1929–39
  • Mussolini: Italy; Il Duce; 1922
  • Hitler: Germany; Chancellor 1933; Führer
  • Mein Kampf — Hitler's book (in prison)
⚔️ WWII Key Events
  • Poland invasion: 1 Sep 1939
  • Pearl Harbor: 7 Dec 1941 (USA joins)
  • Stalingrad: 1942–43 (turning point)
  • D-Day: 6 June 1944 (Normandy)
  • Hiroshima: 6 Aug 1945; Nagasaki: 9 Aug
🌐 UN Formation
  • Charter signed: 26 June 1945 (SF)
  • UN Day: 24 October 1945
  • P5: USA, USSR, UK, France, China
  • 1st SG: Trygve Lie (Norway)
  • Replaced League of Nations
👤 WWII Leaders
  • Hitler — Germany (Nazi)
  • Mussolini — Italy (Fascist)
  • Churchill — UK (Allied)
  • Roosevelt — USA (Allied)
  • Stalin — USSR (Allied after 1941)

📄 Topic-Wise PYQs & Tricky Questions

Q1. The immediate cause of World War I was: CDS PYQ
(a) German invasion of Poland(b) Assassination of Archduke Franz Ferdinand (c) Sinking of the Lusitania(d) Wall Street Crash
✔ Answer: (b) Assassination of Archduke Franz Ferdinand
The assassination of Archduke Franz Ferdinand (heir to the Austro-Hungarian throne) by Gavrilo Princip on 28 June 1914 in Sarajevo was the immediate trigger that set off the chain of alliances leading to WWI. German invasion of Poland triggered WWII (1939). Sinking of Lusitania (1915) helped bring USA into WWI but wasn't the immediate cause. Wall Street Crash was 1929.
Q2. The USA did NOT join the League of Nations because: Tricky
(a) USA was isolationist — Congress refused to ratify(b) Woodrow Wilson opposed it (c) USA was not invited(d) League rejected USA
✔ Answer: (a) USA was isolationist — Congress refused to ratify
The League of Nations was actually proposed by US President Woodrow Wilson (his 14 Points). However, the US Congress refused to ratify the Treaty of Versailles (and thus the League) because of isolationist sentiment — many Americans didn't want to be drawn into future European wars. This was deeply ironic. Wilson won the Nobel Peace Prize for the League concept but his own country never joined.
Q3. 'D-Day' (Operation Overlord) was the Allied invasion of: CDS PYQ
(a) Germany(b) Italy (c) Normandy, France(d) Poland
✔ Answer: (c) Normandy, France
D-Day (6 June 1944) — officially "Operation Overlord" — was the Allied landing on the beaches of Normandy in northwestern France. It was the largest seaborne invasion in history, involving ~156,000 Allied troops from the USA, UK, Canada, and other nations. The successful landing opened the Western Front and led to the liberation of France and ultimately Germany's defeat. Supreme Commander: General Dwight D. Eisenhower.
Q4. Pearl Harbor (7 December 1941) was attacked by: CDS PYQ
(a) Germany(b) Italy (c) Japan(d) Soviet Union
✔ Answer: (c) Japan
Japan attacked the US naval base at Pearl Harbor, Hawaii on 7 December 1941 — a Sunday morning surprise attack. Japan, an Axis power allied with Germany and Italy, aimed to cripple the US Pacific Fleet and buy time to expand in Asia. President Roosevelt called it "a date which will live in infamy." The attack brought the USA into WWII the next day.
Q5. The United Nations was officially formed on: CDS PYQ
(a) 26 June 1945(b) 24 October 1945 (c) 8 May 1945(d) 1 January 1942
✔ Answer: (b) 24 October 1945
The United Nations officially came into existence on 24 October 1945 (UN Day) when the UN Charter was ratified by the required number of nations. The Charter was signed earlier on 26 June 1945 at San Francisco. 8 May 1945 is V-E Day (Germany's surrender). 1 January 1942 was when the "United Nations Declaration" was signed (an earlier Allied agreement during the war, not the UN itself).
Q6. Wall Street Crash (1929) led to the Great Depression, which in turn contributed to: CDS PYQ
(a) End of WWI(b) Rise of Fascism and Nazism (c) Formation of UN(d) Russian Revolution
✔ Answer: (b) Rise of Fascism and Nazism
The Great Depression (1929–39) created mass unemployment and economic despair — particularly devastating in Germany which was already crippled by WWI reparations. This economic desperation made populations receptive to extremist leaders like Hitler (Germany) and Mussolini (Italy) who promised to restore national pride and economic strength. The Depression is considered a key factor in making WWII possible.
Q7. The Battle of Stalingrad (1942–43) is considered a turning point of WWII because: Tricky
(a) It was the first battle of WWII(b) Germany suffered its first major defeat on the Eastern Front (c) USA entered the war here(d) Japan was defeated here
✔ Answer: (b) Germany suffered its first major defeat on the Eastern Front
Battle of Stalingrad (August 1942 – February 1943) is considered the turning point of WWII because it was Germany's first catastrophic defeat on the Eastern Front. The entire German 6th Army (~300,000 soldiers) was surrounded and destroyed. It ended Germany's eastern advance and began the Soviet counter-offensive that eventually reached Berlin. About 2 million casualties total.
Q8. 'Mein Kampf' was written by Hitler while: CDS PYQ
(a) He was Chancellor of Germany(b) He was in prison after the Beer Hall Putsch (c) He was in exile in Austria(d) He was serving in WWI
✔ Answer: (b) He was in prison after the Beer Hall Putsch
Hitler wrote Mein Kampf ("My Struggle") while imprisoned in Landsberg Prison (1923–24) after the failed Beer Hall Putsch (Munich Putsch) on 8–9 November 1923. The book outlined his racist ideology, plans for German expansion (Lebensraum), and his anti-Semitism. He only served 9 months of a 5-year sentence. The book became a bestseller after he came to power in 1933.

📋 Quick Reference — HC20

⚔️ WWI — Basics
  • 1914–1918; MAIN causes
  • Franz Ferdinand shot: 28 June 1914
  • Allied: UK + France + Russia (+ USA 1917)
  • Central: Germany + Austria-Hungary
  • Ended: 11 November 1918
📜 Versailles 1919
  • War guilt — Germany
  • Reparations — £6.6 billion
  • League of Nations (USA refused)
  • Germany lost Alsace-Lorraine
  • Signed 28 June 1919
📉 Interwar
  • Wall Street Crash: 24 Oct 1929
  • Mussolini: Italy; 1922
  • Hitler: Chancellor 1933; Führer
  • Mein Kampf: written in prison (1923)
  • Anschluss (Austria): 1938
⚔️ WWII — Events
  • Poland: 1 Sep 1939 (start)
  • Pearl Harbor: 7 Dec 1941 (USA joins)
  • Stalingrad: 1942–43 (turning point)
  • D-Day: 6 Jun 1944 (Normandy)
  • V-E: 8 May · V-J: 15 Aug 1945
🌐 UN
  • Charter signed: 26 Jun 1945 (SF)
  • UN formed: 24 Oct 1945
  • P5 (veto): USA, USSR, UK, France, China
  • 1st SG: Trygve Lie (Norway)
💣 Atomic Bombs
  • Hiroshima: 6 Aug 1945 ("Little Boy")
  • Nagasaki: 9 Aug 1945 ("Fat Man")
  • Japan surrendered: 15 Aug 1945
  • Ordered by: President Truman
  • Manhattan Project made the bombs
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