Key Idea: This topic is about why 20th-century wars broke out. First you learn a toolkit for classifying wars and sorting their causes, then you apply it to the two great catastrophes of the century: the First World War (1914) and the Second World War (1939). In the Paper 2 essay you compare two wars, so the golden skill is weighing causes — separating the deep, long-term pressures from the short-term spark, and judging which mattered most.
🧰 16.1.1 — Types and causes of war
Not all wars look the same, and historians classify them by how they are fought. Getting the type right shapes your whole essay, because a war fought inside one country breaks out very differently from one where a whole nation mobilises.
Wars also almost never have a single cause. Historians sort reasons into five categories (remember E-I-P-T-R) and by timing — deep long-term pressures versus the short-term spark, called the catalyst or trigger.
- Four types of war — civil (groups fight for control inside one country, e.g. Spain 1936–39); guerrilla (small mobile fighters using ambush and hit-and-run); limited (restricted aims and weapons, e.g. Korea 1950–53); total (the whole society mobilised and civilians targeted, e.g. WWII).
- E-I-P-T-R categories of cause — Economic (resources, depression), Ideological (fascism, communism, nationalism), Political (weak states, leaders' ambitions), Territorial (land and borders), Religious (faith or sectarian division).
- Cause vs catalyst — a cause is a reason the war happened; a catalyst/trigger is only the spark that set it off. Remove the trigger and the war likely still comes; remove the deep causes and the trigger changes nothing.
- Long-term vs short-term — long-term (underlying) pressures build for years and make war likely; short-term (immediate) events turn tension into fighting.
- Historians weigh, they don't list — a top answer names the most important cause and explains why it outweighs the others.
🔥 16.1.2 — Causes of the First World War
By 1914 Europe was a powder keg. The long-term causes are remembered as M-A-I-N: Militarism (glorifying armies and having war plans ready), Alliances (promises to defend each other), Imperialism (colonial rivalry) and Nationalism (fierce national pride).
These split Europe into two armed camps — the Triple Alliance (Germany, Austria-Hungary, Italy) and the Triple Entente (France, Russia, Britain). Then, on 28 June 1914, Gavrilo Princip assassinated Archduke Franz Ferdinand at Sarajevo, and the July Crisis slid the continent into war.
- M-A-I-N long-term causes — Militarism (the Anglo-German naval race and Dreadnoughts), Alliances (two armed blocs), Imperialism (Germany felt encircled), Nationalism (Balkan and Pan-Slav pride was the flashpoint).
- The rivalries — France wanted revenge for Alsace-Lorraine (lost in 1871); Britain and Germany raced to build battleships; Austria and Russia both wanted the Balkans as the Ottoman Empire crumbled.
- The trigger — Princip, a Bosnian Serb, shot Franz Ferdinand at Sarajevo, 28 June 1914. This was the spark, not the cause.
- The July Crisis slide — Germany's 'blank cheque' to Austria → Austria's harsh ultimatum to Serbia → Russian mobilisation → chain of war declarations.
- Britain joins — Germany's Schlieffen Plan invaded neutral Belgium on 4 August 1914; Britain had pledged to defend Belgium, so it declared war.
⚔️ 16.1.3 — Causes of the Second World War
Just twenty years later, war returned. Remember the causes as L-I-T: Long-term wounds (the Treaty of Versailles, a weak League of Nations, the Great Depression), Ideological drives (Nazi, Fascist and militarist beliefs), and the Trigger (the invasion of Poland).
The 1919 Versailles treaty blamed Germany, took its land, and demanded huge reparations — anger Hitler later used. From 1936 he took bolder and bolder gambles while Britain and France chose appeasement (giving in to avoid war), until Germany invaded Poland.
- Long-term (L) — resentment at the Treaty of Versailles (1919); the League of Nations failed at Manchuria (1931) and Abyssinia (1935); the Great Depression (after 1929) helped Hitler to power in 1933.
- Ideological (I) — Nazi Lebensraum ('living space' in the east), Italian Fascism (Mussolini's new Roman Empire), and Japanese militarism (Manchuria 1931, China 1937).
- Expansion and appeasement — Rhineland (1936) → Anschluss with Austria (1938) → Munich Agreement handing over the Sudetenland (Sept 1938) → seizing all of Prague (March 1939).
- Nazi–Soviet Pact (Aug 1939) — Germany and the USSR agreed not to fight and secretly carved up Poland, freeing Hitler from a two-front war — the final green light.
- Trigger and global war — Germany invaded Poland on 1 September 1939; Britain and France declared war on 3 September 1939. Pearl Harbor (Dec 1941) brought in the USA and made the war global.
✍️ Exam-ready answers
To what extent was the alliance system responsible for the outbreak of the First World War?
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Compare and contrast the causes of two 20th-century wars, each chosen from a different region.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
🎯 One-glance recall
The toolkit: types + E-I-P-T-R + trigger Four types of war: civil, guerrilla, limited, total. Five cause categories: Economic, Ideological, Political, Territorial, Religious. Sort causes by timing into long-term (underlying) and short-term, and never confuse a cause with the catalyst/trigger — the spark that lights an already-loaded fuse.
WWI: M-A-I-N loaded the gun, Sarajevo fired it Long-term causes were Militarism, Alliances, Imperialism and Nationalism, splitting Europe into the Triple Alliance vs Triple Entente. The trigger was Princip's assassination of Franz Ferdinand at Sarajevo on 28 June 1914. The July Crisis (blank cheque → ultimatum → Russian mobilisation) and the Schlieffen Plan's invasion of Belgium on 4 August 1914 brought Britain in.
WWII: L-I-T — a bitter peace and a bold dictator Long-term: resentment at the Treaty of Versailles (1919), a weak League of Nations, and the Great Depression. Ideological: Nazi Lebensraum, Italian Fascism, Japanese militarism. Hitler's expansion (Rhineland 1936, Anschluss 1938, Munich/Sudetenland 1938, Prague 1939) met appeasement; the Nazi–Soviet Pact (Aug 1939) cleared the way, and the invasion of Poland on 1 September 1939 was the trigger.
The exam move: weigh, don't narrate Paper 2 is essay-based, comparing two wars from different regions. Command terms like 'To what extent', 'Examine', 'Evaluate' and 'Compare and contrast' all demand a weighed judgement. Structure thematically, separate long-term causes from the trigger, and always argue which cause mattered most rather than retelling the story.