THE INTERWAR PERIOD (1919–1939)

1. INTRODUCTION

The Interwar Period, spanning from the end of the First World War in 1918 to the outbreak of the Second World War in 1939, was a time of profound political, economic, and social transformation. Europe emerged devastated from the Great War, burdened by human losses, material destruction, and economic instability. The Paris Peace System sought to reorganize the continent and prevent future conflicts; however, its punitive terms, especially those imposed on Germany, generated deep resentment.

This era witnessed the collapse of long-standing empires, the rise of new nation-states, the spread of democratic experiments, and the emergence of extremist ideologies such as fascism, Nazism, and Stalinist communism. Economic crises—most notably the Great Depression—further destabilized societies and paved the way for authoritarian regimes. The period ultimately culminated in global confrontation once diplomacy and collective security mechanisms failed.

2. THE POSTWAR SETTLEMENT AND THE PARIS PEACE SYSTEM

A) THE PEACE TREATIES (1919–1923)

The Paris Peace Conference (1919–1920) produced a complex system of treaties that reshaped Europe and the Middle East:

• Treaty of Versailles (1919): Placed full responsibility for the war on Germany, imposed territorial losses (Alsace-Lorraine, Polish Corridor), military restrictions, and heavy reparations.
  
  

• Treaty of Saint-Germain (1919): Formal dissolution of the Austro-Hungarian Empire; creation of Austria and recognition of new states (Czechoslovakia, Yugoslavia).
  
  

• Treaty of Trianon (1920): Reduced Hungary’s territory by two-thirds.
  
  

• Treaty of Neuilly (1919): Sanctions on Bulgaria.
  
  

• Treaty of Sèvres (1920) and Treaty of Lausanne (1923): Disintegration and reorganization of the Ottoman Empire; recognition of modern Turkey under Mustafa Kemal Atatürk.
  
  

B) THE LEAGUE OF NATIONS

Created under President Woodrow Wilson’s Fourteen Points, the League aimed to maintain collective security through diplomacy, sanctions, and arbitration. However, it faced key limitations:

• Absence of major powers at decisive moments (USA never joined).
  
  

• Limited enforcement mechanisms.
  
  

• Inability to act decisively during the crises of the 1930s (Manchuria, Abyssinia).
  
  

3. POLITICAL INSTABILITY AND THE CRISIS OF DEMOCRACY

A) WEIMAR GERMANY (1919–1933)

The new German Republic faced enormous challenges:

• Hyperinflation crisis of 1923.
  
  

• Political extremism, with uprisings by communists and right-wing paramilitaries.
  
  

• Economic stabilization under the Dawes Plan (1924).
  
  

• Brief period of prosperity followed by collapse during the Great Depression.
  
  

• Rise of Adolf Hitler and the Nazi Party from 1930 onwards.
  
  

B) EASTERN EUROPE AND THE NEW NATION-STATES

Newly created states—Poland, Czechoslovakia, Yugoslavia, and the Baltic republics—struggled with:

• Ethnic diversity and minority conflicts.
  
  

• Weak parliamentary traditions.
  
  

• Increasing authoritarian tendencies (e.g., Poland under Pilsudski, Hungary under Horthy).
  
  

C) THE CRISIS OF PARLIAMENTARY LIBERALISM

Even consolidated democracies such as France and the United Kingdom experienced internal political tensions, economic instability, and radical movements. In contrast, authoritarian models gained traction as solutions to disorder.

4. THE RISE OF TOTALITARIAN IDEOLOGIES

A) FASCIST ITALY

Benito Mussolini and his Fascist Party seized power in 1922 through political violence and mass mobilization. Key elements of fascism included:

• Dictatorship centered on the Duce.
  
  

• Corporatist economic model.
  
  

• Militarism and expansionist ambitions (invasion of Ethiopia, 1935).
  
  

B) NAZI GERMANY

Adolf Hitler, appointed Chancellor in 1933, established a totalitarian regime characterized by:

• Racial ideology and antisemitism.
  
  

• Suppression of opposition (Reichstag Fire, enabling laws).
  
  

• Economic recovery based on rearmament and state intervention.
  
  

• Expansionist policies: remilitarization of the Rhineland (1936), Anschluss (1938), Sudeten crisis (1938).
  
  

C) THE SOVIET UNION UNDER STALIN

After Lenin’s death in 1924, Stalin consolidated absolute control over the Communist Party and the state:

• Forced collectivization and industrialization (Five-Year Plans).
  
  

• Great Purges (1936–1938).
  
  

• Establishment of a centralized one-party dictatorship.
  
  

5. THE GLOBAL ECONOMIC CRISIS: THE GREAT DEPRESSION (1929–1939)

A) ORIGINS

The Wall Street Crash of October 1929 triggered a global financial collapse due to interconnected markets.

B) ECONOMIC CONSEQUENCES

• Collapse of industrial production.
  
  

• Mass unemployment (over 30% in some countries).
  
  

• Sharp decline in international trade.
  
  

C) POLITICAL CONSEQUENCES

• Growth of extremist movements.
  
  

• Weakening of democratic governments.
  
  

• Strengthening of authoritarian regimes (Nazism, fascism).
  
  

• New Deal reforms in the United States under Franklin D. Roosevelt (1933).
  
  

6. INTERNATIONAL TENSIONS AND THE BREAKDOWN OF COLLECTIVE SECURITY

A) JAPANESE EXPANSIONISM

• Invasion of Manchuria (1931).
  
  

• Establishment of Manchukuo (1932).
  
  

• Withdrawal from the League of Nations (1933).
  
  

B) ITALIAN EXPANSIONISM

• Conquest of Ethiopia (1935).
  
  

• Closer alliance with Nazi Germany (Rome–Berlin Axis, 1936).
  
  

C) NAZI AGGRESSION

• Remilitarization of the Rhineland (1936).
  
  

• Anschluss with Austria (1938).
  
  

• Demands on Sudetenland (1938).
  
  

• Occupation of Czechoslovakia (1939).
  
  

D) THE SPANISH CIVIL WAR (1936–1939)

A symbolic confrontation between fascism and republican democracy:

• German and Italian support for Franco.
  
  

• Soviet aid for the Republicans.
  
  

• Victory of Franco’s authoritarian regime.
  
  

E) THE ROAD TO WAR

• Nazi–Soviet Pact (August 1939).
  
  

• Invasion of Poland (September 1, 1939).
  
  

• Britain and France declared war, marking the beginning of WWII.
  
  

7. SOCIAL AND CULTURAL TRANSFORMATIONS

A) SCIENTIFIC AND TECHNOLOGICAL ADVANCES

• Development of quantum physics.
  
  

• Innovations in medicine and aviation.
  
  

B) CULTURAL MOVEMENTS

• Surrealism and modernist art.
  
  

• Bauhaus architecture.
  
  

• Jazz, cinema, and mass entertainment.
  
  

C) CHANGES IN SOCIETY

• Urbanization and consumer culture.
  
  

• Expansion of women's political rights.
  
  

• Emergence of youth and mass culture.
  
  

8. HISTORICAL SIGNIFICANCE OF THE INTERWAR PERIOD

The Interwar Period was a crucial transitional era that shaped the political, social, and ideological landscape of the 20th century. The failure of peace treaties, combined with economic depression and political extremism, created conditions for the rise of aggressive totalitarian regimes. The collapse of collective security directly led to the outbreak of the Second World War. Meanwhile, cultural and intellectual life experienced profound creative innovation whose influence persists today.

1. MAIN HISTORICAL FIGURES

• Benito Mussolini
  
  

• Adolf Hitler
  
  

• Joseph Stalin
  
  

• Franklin D. Roosevelt
  
  

• Neville Chamberlain
  
  

• Winston Churchill (in opposition)
  
  

• Léon Blum (Popular Front, France)
  
  

• Mustafa Kemal Atatürk
  
  

• Emperor Hirohito and Japanese militarist leaders
  
  

2. TREATIES AND AGREEMENTS

• Treaty of Versailles (1919)
  
  

• Locarno Treaties (1925)
  
  

• Kellogg–Briand Pact (1928)
  
  

• Munich Agreement (1938)
  
  

• Nazi–Soviet Pact (1939)
  
  

3. KEY DATES

• 1919–1920: Paris Peace Conference
  
  

• 1922: Mussolini in power
  
  

• 1923: Hyperinflation in Germany
  
  

• 1929: Wall Street Crash
  
  

• 1933: Hitler becomes Chancellor
  
  

• 1936–1939: Spanish Civil War
  
  

• 1938: Munich Agreement
  
  

• 1939: Invasion of Poland
  
  

4. MAJOR CRISES

• Ruhr Crisis (1923)
  
  

• Manchurian Crisis (1931)
  
  

• Abyssinia Crisis (1935)
  
  

• Sudeten Crisis (1938)
  
  

5. IDEOLOGIES

• Fascism
  
  

• Nazism
  
  

• Communism (Stalinism)
  
  

• Social democracy
  
  

• Liberalism