Causes of Major Conflicts: Why Do Large-Scale Wars Begin?
- Wars start when long-term tensions and short-term triggers collide.
- WWI and WWII show how rivalry, pride, fear, and bad diplomacy can transform a local crisis into a global catastrophe.
- Understanding these patterns helps explain the entire 20th century, and many conflicts today.
- Shaking a bottle of soda
- Long-term causes = shaking the bottle for years (arms races, hatred, humiliation, alliances).
- Short-term cause = opening the bottle suddenly (Sarajevo assassination, Rhineland, Poland).
- When the pressure inside is already extreme, even a tiny action makes everything explode.
Key Factors That Led to WWI (Long-Term Causes)
Nationalism
- Nationalism made countries emotionally invested in proving their strength, superiority, and independence. It wasn’t just politics, it was pride.
- Germany, France, Russia, and Britain all had strong national identities and wanted to protect or expand their influence.
- Serbian nationalism was especially intense. Serbia wanted to unite all Serbs into one “Greater Serbia,” including those living inside Austria-Hungary. This directly threatened Austria-Hungary’s control over the Balkans.
- France had never accepted losing Alsace-Lorraine to Germany in 1871. Regaining this territory became a national mission: a symbol of French pride and revenge.
- Across Europe, schoolbooks, newspapers, and propaganda reinforced the idea that defending the nation, even through war, was honorable and necessary.
Militarism
- Militarism is the belief that strong armed forces are essential for national greatness. By 1914, European countries valued military power as much as economic or political strength.
- Governments invested heavily in new weapons, including machine guns, long-range artillery, and modern battleships.
- Germany and Britain entered into a massive naval arms race, each trying to outproduce the other. Germany built Dreadnought-type battleships to challenge Britain’s dominant navy, something Britain saw as a direct threat to its empire.
- Military leaders gained huge political influence. In many countries, generals were listened to more than diplomats, making peaceful solutions less likely.
- War was increasingly seen as inevitable, a test of national strength rather than a tragedy to avoid.
Imperialism
Imperialism
Imperialism is when a powerful country extends its control over weaker regions or countries, usually to gain resources, land, wealth, or strategic advantage. This control can be political, economic, or military, and often involves ruling the territory as a colony.
Example
- Expansion of territory
- Control of resources and trade
- Political domination over local governments
- Cultural influence or pressure
- Often justified as “civilising,” but usually exploitative
- European powers competed for colonies in Africa, Asia, and the Middle East. The more territory you had, the more powerful you were seen to be.
- This created jealousy and suspicion. Germany entered the imperial race late and felt “cheated” compared to Britain and France, increasing resentment.
- Conflicts over territory, such as the Moroccan Crises (1905 and 1911), where Germany challenged France’s control of Morocco, brought Europe close to war even before 1914.
- Imperial competition made nations view each other as rivals, not partners. Every gain by one empire felt like a loss for another.
Alliances
- To protect themselves, European powers formed defensive alliances. But instead of creating safety, these alliances created rigid blocs.
- Triple Alliance: Germany, Austria-Hungary, Italy
- Triple Entente: Britain, France, Russia
- Each alliance promised military support if a member was attacked. This meant a small dispute involving two countries could quickly drag in six or more nations.
- Alliances encouraged risky behaviour: leaders acted more aggressively because they believed their partners would back them.
- By 1914, Europe was split into two powerful camps facing each other, making war far more likely if any spark appeared.
Balkan Tensions
- The Ottoman Empire was weakening (“the sick man of Europe”), leaving a power vacuum in the Balkans.
- Different ethnic groups wanted independence, while larger powers wanted influence.
- Serbia saw itself as the leader of Slavic peoples and wanted to expand.
- Austria-Hungary feared Serbian nationalism because it threatened the unity of its multi-ethnic empire.
- Russia supported Serbia because both were Slavic and Orthodox Christian, giving Serbia a powerful ally.
- The region became a hotbed of assassinations, rebellions, and border disputes, making it the most unstable part of Europe.
- Two Balkan Wars (1912–13) had already shown how explosive the region was, and Europe watched nervously as tensions grew.
Short-Term Causes of WWI
- Bosnian Crisis (1908)
- Austria-Hungary annexed Bosnia.
- Serbia and Russia were angered; Austria grew more confident.
- Increased tension in the Balkans.
- Moroccan Crises (1905 & 1911)
- Germany challenged France in Morocco.
- Britain supported France, strengthening their alliance.
- Germany felt isolated and resentful.
- Balkan Wars (1912–1913)
- Balkan states defeated the Ottoman Empire.
- Serbia became stronger, worrying Austria-Hungary.
- Austria determined to weaken Serbia.
- Assassination of Franz Ferdinand (June 1914)
- Murdered by Gavrilo Princip, a Bosnian Serb nationalist.
- Austria-Hungary blamed Serbia.
- July Crisis (July 1914)
- Austria, backed by Germany, sent Serbia a harsh ultimatum.
- Russia mobilised; Germany mobilised; alliances activated.
- Germany invaded Belgium → Britain declared war.
Key Events That Led to WWII (Long-Term Causes)
Treaty of Versailles Resentment
- Germany felt the treaty was a Diktat: a dictated peace they had no say in.
- Reparations were enormous (132 billion gold marks), creating long-term economic strain and humiliation.
- Germany lost 13% of its land and 10% of its population, including industrial areas like the Saar and Alsace–Lorraine.
- The war guilt clause (Article 231) blamed Germany entirely for WWI, which many Germans saw as unfair and insulting.
- The German army was limited to 100,000 men, with no tanks, aircraft, or submarines, seen as a national embarrassment.
- This anger weakened the new Weimar Republic, which was blamed for accepting the treaty, making it an easy target for extremists.
- Parties like the Nazis capitalised on resentment, promising to tear up Versailles and restore German pride.
Rise of Fascism
- Fascism grew in countries that felt humiliated, economically unstable, or ignored by major powers.
- Hitler in Germany used promises of “restoring greatness,” overturning Versailles, and expanding for Lebensraum (living space).
- Mussolini in Italy argued Italy had been “cheated” of land after WWI and needed a new Roman Empire.
- Japanese militarists believed Japan needed to dominate Asia to secure resources and prestige.
- These leaders promoted ultra-nationalism, militarism, and a belief that war was natural and necessary.
- Dictatorships allowed fast rearmament and expansion without political opposition.
Great Depression (1929)
- The global economic collapse caused mass unemployment, poverty, and political chaos.
- Democracies struggled to respond quickly, leading many people to turn to extreme solutions offered by fascists and militarists.
- In Germany, the Depression destroyed the economy:
- Millions unemployed → desperation for radical change
- Nazi Party used propaganda blaming Jews, communists, and Versailles
- In Japan, economic hardship pushed the military to argue that Japan needed to invade nearby countries for coal, iron, land, and food.
- Economic crisis destabilised international relations, making cooperation difficult and aggression more attractive.
Failure of the League of Nations
- The League lacked an army, so it relied on members to enforce decisions, but they rarely acted.
- Japan invades Manchuria (1931):
- League condemned Japan but did nothing.
- Japan simply left the League.
- Italy invades Ethiopia (1935):
- League imposed weak sanctions that did not include oil.
- Britain and France secretly tried to appease Mussolini.
- These failures showed dictators that the League was toothless.
- The message was simple: You can break international law and get away with it.
German Rearmament
- Hitler openly defied Versailles by rebuilding the army, air force (Luftwaffe), and navy.
- In 1935, Germany introduced conscription and expanded the army to 500,000 soldiers.
- Britain and France protested but avoided confrontation, still traumatised by WWI.
- This led to appeasement, a policy based on the belief that giving Hitler small concessions would prevent another war.
- Rearmament boosted Germany’s economy and national pride, strengthening Hitler’s popularity.
- Once Hitler realised the Allies would not intervene, he became bolder:
- Remilitarised the Rhineland (1936)
- Formed alliances with Italy and Japan
- Planned expansion into Eastern Europe
Short-Term Causes of WWII
- Remilitarisation of the Rhineland (1936)
- Hitler sent German troops into the Rhineland, which violated the Treaty of Versailles and the Locarno Treaties.
- France and Britain did nothing due to fear of war and their own internal issues.
- Hitler grew more confident, believing the Allies would not stop him.
- Anschluss with Austria (March 1938)
- Hitler encouraged Austrian Nazis to create unrest.
- He pressured the Austrian chancellor into allowing German troops to enter.
- A manipulated referendum showed support for union with Germany.
- The Anschluss violated Versailles, but again Britain and France did not intervene.
- The Sudetenland Crisis (1938)
- Hitler demanded the Sudetenland, a German-speaking region of Czechoslovakia.
- Czechoslovakia was ready to defend itself, but Britain and France wanted to avoid war.
- Munich Agreement (Sept 1938): Britain and France gave Hitler the Sudetenland (appeasement).
- Hitler promised he had “no more territorial demands.”
- Occupation of the Rest of Czechoslovakia (March 1939)
- Hitler broke his Munich promise and took all of Czechoslovakia.
- This was the first time he seized non-German territory.
- Britain and France realised appeasement had failed and guaranteed Poland's borders.
- Nazi–Soviet Pact (Aug 1939)
- A non-aggression pact between Germany and the USSR.
- Included a secret clause to divide Poland between them.
- Shocked Europe because Hitler and Stalin were ideological enemies.
- Gave Hitler confidence to invade Poland without fear of Soviet intervention.
- Invasion of Poland (1 September 1939)
- Germany used the pact to attack Poland from the west.
- Britain and France had promised to defend Poland.
- 3 September 1939: Britain and France declared war on Germany.
- This marked the official start of World War II.
- Japan’s Expansion in Asia
- Economic Crisis and Rise of Militarism (1929–1932)
- Japan’s economy collapsed after the Wall Street Crash, as demand for silk from the USA fell.
- Factories closed and peasants starved, undermining confidence in democracy.
- The army gained political power, blaming the USA for Japan’s economic problems.
- In 1931, the Japanese army invaded Manchuria without government approval, showing militarists were now in control.
- Invasion of China (1937)
- Japan launched a full-scale invasion of China, capturing Shanghai and Nanjing.
- China refused to surrender, leading to a long and costly war.
- Japan remained heavily dependent on US oil (80%) to sustain its military campaign.
- Breakdown in US–Japan Relations (1939–1941)
- The USA imposed trade sanctions in 1939 when Japan ignored warnings to stop the war in China.
- In 1941, Japan invaded Indo-China to gain resources, prompting Roosevelt to ban all trade, including oil.
- The embargo threatened Japan’s war effort and increased tensions further.
- Attack on Pearl Harbor (December 1941)
- Japan launched a surprise attack on Pearl Harbor to prevent the USA from interfering in Asia.
- The USA declared war on Japan the next day.
- Shortly afterward, Hitler declared war on the USA, escalating WWII into a global conflict.
- Economic Crisis and Rise of Militarism (1929–1932)
Other Types of Wars in the 20th Century
- Civil Wars
- Russian Civil War (1917–22)
- Chinese Civil War (1927–49)
- Spanish Civil War (1936–39)
- Cold War Proxy Wars
- Korean War (1950–53)
- Vietnam War (1955–75)
- Soviet–Afghan War (1979–89)
- Decolonisation Wars
- Algeria vs France (1954–62)
- Kenya Mau Mau Uprising (1952–60)
- Vietnam vs France (1946–54)
- Ethnic/Regional Conflicts
- Israel–Arab wars
- Indo–Pakistan wars
- Yugoslav Wars (1991–95)
- Rwanda (1994)
- Guerrilla/Revolutionary Movements
- Cuban Revolution (1953–59)
- African and Latin American liberation movements.
- Timeline: Major Conflicts & Key Turning Points (1870–1950)
- Before WWI
- 1871: Germany unifies → massive shift in European power.
- 1882: Triple Alliance formed.
- 1907: Triple Entente formed.
- 1911–13: Balkan Wars → region destabilised.
- 28 June 1914: Franz Ferdinand assassinated.
- WWI (1914–1918)
- July–Aug 1914: Alliance chain reaction → world war begins.
- 1914–15: Trench warfare dominates Western Front.
- 1916: Battles of Somme & Verdun.
- 1917: US enters war; Russia leaves after revolution.
- 11 Nov 1918: Armistice signed.
- After WWI
- 1919: Treaty of Versailles.
- 1920: League of Nations created.
- 1923: Hyperinflation in Germany weakens Weimar government.
- 1929: Great Depression begins.
- Lead-Up to WWII
- 1931: Japan invades Manchuria.
- 1933: Hitler becomes Chancellor.
- 1935–36: Italy invades Ethiopia; Germany remilitarises Rhineland.
- 1937: Japan invades China.
- 1938: Anschluss + Sudetenland (Munich).
- 1939 (March): Germany takes all of Czechoslovakia.
- 1939 (Aug): Nazi–Soviet Pact.
- 1939 (1 Sept): Invasion of Poland → WWII begins.
- WWII (1939–1945)
- 1940: Germany captures France.
- 1941 (June): Germany invades USSR.
- 1941 (Dec): Pearl Harbor → USA enters war.
- 1944 (June): D-Day landings.
- May 1945: Germany surrenders.
- Aug 1945: Atomic bombs dropped → Japan surrenders.
- Before WWI
- Why did nationalism and imperialism make Europe more unstable before WWI?
- How did the alliance system turn a regional crisis into a world war in 1914?
- What made the Treaty of Versailles a long-term cause of WWII?
- Why was the Great Depression such a powerful driver of extremism?
- How did appeasement contribute to the outbreak of WWII?
- Why was the Nazi–Soviet Pact such a shocking and dangerous development?
- How are civil wars and proxy wars different from world wars?
- Which type of 20th-century conflict do you think caused the most lasting change, and why?
- Across WWI and WWII you can see the same patterns repeat:
- Rivalry
- National humiliation
- Arms races
- Alliance systems
- Weak diplomacy
- Leaders taking risks
- International organisations failing
- Once you spot the pattern, it becomes much easier to explain why conflicts escalate.