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Why this micro matters: Paper 2 is a World History essay paper. You study one theme — here, the causes and effects of 20th-century wars — and in the exam you compare two wars from different regions.
Before you can explain why a war happened, you need a shared vocabulary: what type of war it was, and what kinds of cause to look for. This section gives you the toolkit.
Not all wars look the same. The IB expects you to know four types of war and to describe each one clearly.
Getting the type right shapes your whole essay, because a civil war and a total war break out — and end — for very different reasons.
- Civil war — fighting between organised groups inside the same country for control of the state. Example: the Spanish Civil War (1936–39) and the Chinese Civil War (1927–49).
- Guerrilla war — small, mobile fighters use ambushes, sabotage and hit-and-run raids instead of open battle, usually against a stronger regular army. Example: the Chinese Communists under Mao, or the Vietcong.
- Limited war — states fight for restricted aims with restricted means, deliberately not using their full power. Example: the Korean War (1950–53), kept limited to avoid a wider nuclear clash.
- Total war — a state mobilises its entire society — economy, industry, civilians and propaganda — and targets the enemy's whole population, not just its army. Example: the Second World War (1939–45).
Limited war
- Restricted aims (e.g. defend a border, not destroy the enemy)
- Restricted weapons and manpower held back on purpose
- Civilians largely outside the fighting
- Often ends in a negotiated settlement — Korea, 1953
Total war
- Aim is the enemy's complete defeat or surrender
- Whole economy and population mobilised for the war effort
- Civilians become targets — bombing, blockade, occupation
- Usually ends only in one side's collapse — WWII, 1945
The types can overlap: A single conflict can be more than one type at once.
The Chinese Civil War was a civil war fought largely with guerrilla methods. Vietnam was a guerrilla war that was also, for the Vietnamese, a total war. When you label a war, say which features make it that type — don't just stick on a one-word tag.
How this is tested: Some Paper 2 questions ask directly about type — for example, 'Compare and contrast the nature of two 20th-century wars' or 'To what extent was one war you have studied a total war?'
Knowing the defining features lets you argue, not just assert.
Wars almost never have a single cause. Historians sort the reasons into categories so that nothing important gets missed.
The IB names five you should always check for: economic, ideological, political, territorial and religious.
Economic causes
The drive for resources, markets, trade routes or wealth — or the instability caused by a slump. The Great Depression fuelled aggression in Germany and Japan in the 1930s.
Ideological causes
Clashing belief systems — fascism, communism, nationalism, democracy — that make each side see the other as a threat to be destroyed. Central to the Spanish Civil War and the Cold War.
Political causes
Weak governments, power struggles, unstable new states, the ambitions of leaders, or the collapse of alliances and diplomacy. Think of a dictator gambling on war to unite a divided nation.
Territorial causes
Disputes over land and borders — reclaiming 'lost' territory, seizing living-space, or controlling a strategic region. Hitler's demand for Lebensraum is the classic case.
Religious causes
Conflict rooted in faith or sectarian division. Rarer as a main cause in 20th-century wars, but it can sharpen ethnic and national hatreds — as in later conflicts in the Balkans.
E-I-P-T-R: Economic · Ideological · Political · Territorial · Religious — run through all five for every war.
Causes work together, not alone: The categories are a checklist, not separate boxes. In a real war they feed into each other.
German ideology demanded territory in the east; economic pressure made that land look essential; and Hitler's political ambition tied it all together. A strong essay shows the links, not just a list.
| Category | What to look for | Quick example |
|---|---|---|
| Economic | Resources, markets, depression, rearmament | Japan's hunt for oil and raw materials |
| Ideological | Fascism, communism, nationalism, democracy | Fascists vs Republicans in Spain |
| Political | Weak states, leaders' ambitions, failed diplomacy | Collapse of appeasement in 1939 |
| Territorial | Borders, lost land, living-space, strategy | Hitler's demand for Lebensraum |
| Religious | Faith or sectarian division | Sharpening ethnic conflict in the Balkans |
Match causes to type: The category often hints at the type. Ideological splits inside one country tend to produce civil wars; territorial greed between states tends toward total war. Use both frameworks together.
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The most important skill in Paper 2 causation is weighing causes — deciding which mattered most.
To do that, historians split causes by when they acted: long-term pressures building over years, and short-term events that set the war off.
Long-term (underlying) causes
Deep pressures building for years or decades — economic weakness, ideological hatred, unresolved territorial grievances. They make a war likely but do not fix its exact date.
Short-term (immediate) causes
Events in the final months or weeks that turn tension into fighting — a failed negotiation, a mobilisation, a provocative move by a leader.
Catalyst / trigger
The single spark that lights the fuse — an assassination, an invasion, an incident. It starts the war but rarely explains it on its own.
Cause vs catalyst — the key distinction: A cause is a reason the war happened; a catalyst is merely what set it off at that moment.
The classic test: Germany's invasion of Poland on 1 September 1939 triggered Britain and France to declare war — but the real causes were the Treaty of Versailles, the Depression, Nazi ideology and years of failed appeasement. Remove the trigger and the war still likely comes; remove the deep causes and the trigger changes nothing.
Historians weigh, they don't just list: Historians argue about relative importance. Some stress structural long-term forces (economics, ideology); others stress individual leaders and contingency — the idea that things could have gone differently.
A top essay names a factor as most important, explains why it outweighs the others, and shows how the trigger only worked because the deeper causes were already in place.
Common mistake: Do not confuse the trigger with the main cause. Writing 'the war was caused by the invasion of Poland' is describing the spark, not explaining the war. Always dig down to the long-term pressures behind the trigger.
- Ask 'why then?' — the trigger answers the timing; the deep causes answer why at all.
- Ask 'why here?' — territorial and political causes often explain the location of a conflict.
- Ask 'most important?' — always reach a judgement, ranking the causes rather than listing them.