Paper 2: 20th-Century Wars — Causes of War

· Exact syllabus location: Paper 2, World history topic 11: Causes and effects of 20th-century wars, subtopic Causes of war.
· Official syllabus focus: students must understand economic, ideological, political, territorial and other causes, plus short-term and long-term causes of 20th-century wars.
· Main exam expectation: answers must use specific 20th-century wars, not general claims about conflict.
· Comparison requirement: Paper 2 questions may require examples from two different regions of the world. The IB regions are Africa and the Middle East, the Americas, Asia and Oceania, and Europe.
· Suggested examples are not compulsory: the syllabus gives examples such as Spanish Civil War (1936–1939), Chinese Civil War (1927–1937 and/or 1946–1949), Vietnam (1946–1954 and/or 1964–1975), Algerian War (1954–1962), Iran–Iraq War (1980–1988), Falklands/Malvinas War (1982), First World War (1914–1918) and Second World War (1939–1945), but teachers may choose other suitable wars.
· Cross-regional warning: if using a cross-regional war such as the First World War or Second World War, use it in one regional context only in the same essay, for example Second World War in the Pacific, not also Second World War in Europe.

What “causes of war” means in IB essays

· The subtopic is about explaining why war broke out, not narrating how the war was fought or what happened afterwards.
· Strong answers distinguish between long-term causes that created tension, short-term causes that intensified crisis, and immediate triggers that turned tension into war.
· IB essays reward causation and judgement: students should argue which causes were most significant, necessary, sufficient, or interconnected.
· Avoid treating categories separately if they overlapped: territorial disputes often had ideological, economic and political dimensions.
· The best essays compare wars by asking whether their causes were mainly structural or contingent: for example, long-term nationalism versus a short-term diplomatic crisis.

Cause category 1: Political and territorial causes

· Political causes include struggles for power, weak governments, disputed legitimacy, state collapse, authoritarian ambitions, and revolutionary instability.
· Territorial causes include border disputes, lost provinces, empire, annexation, secession, or competition over strategically important land.
· These causes are often strongest when territory becomes tied to national prestige, security, or state survival.
· In essays, use this category to show how leaders and states turned political insecurity into armed conflict.

· First World War (1914–1918), Europe: rivalry between alliance blocs, crises in the Balkans, and disputes over influence created a political and territorial setting in which the assassination of Archduke Franz Ferdinand became an immediate trigger. Use this to argue that the war cannot be explained by the assassination alone; the trigger mattered because of the wider long-term alliance and imperial rivalry system.
· Falklands/Malvinas War (1982), the Americas: the territorial dispute over the Falklands/Malvinas Islands was central, but the Argentine military junta’s political need for legitimacy made war more likely. Use this to show how a territorial claim can become explosive when combined with domestic political weakness.
· Iran–Iraq War (1980–1988), Africa and the Middle East: territorial disputes over the Shatt al-Arab waterway combined with Saddam Hussein’s political calculation after the 1979 Iranian Revolution. Use this to argue that territorial disputes may be longstanding, but war often depends on a leader’s short-term judgement that the opponent is vulnerable.
· Chinese Civil War (1927–1937 and/or 1946–1949), Asia and Oceania: conflict between the Guomindang and Chinese Communist Party reflected rival claims to political legitimacy and control of the Chinese state. Use this as a civil-war example where the central issue was not foreign territory but who had the right to rule.

This map shows the alliance structure in Europe before the First World War. Use it to visualise why a Balkan crisis could escalate into a wider European war through alliance commitments and security fears. Source

Cause category 2: Ideological causes

· Ideological causes involve conflict over political belief systems, such as communism, fascism, nationalism, anti-colonialism, or competing visions of state and society.
· Ideology can cause war directly when groups see compromise as impossible, or indirectly by intensifying fear and propaganda.
· In IB essays, do not simply name an ideology; explain how it created enemy images, mobilised support, or justified violence.

· Spanish Civil War (1936–1939), Europe: conflict between Republicans and Nationalists became a clash involving left-wing republicanism, socialism, anarchism, communism, conservatism, Catholic traditionalism and fascism. Use this to argue that ideology polarised Spanish society and made compromise harder, but it should be linked to political instability and social conflict.
· Chinese Civil War (1927–1937 and/or 1946–1949), Asia and Oceania: rivalry between the Guomindang and Chinese Communist Party was ideological as well as political. Use this to compare with Spain: both had ideological polarisation, but China’s civil war also depended heavily on state weakness, rural conditions and the impact of Japanese invasion.
· Vietnam (1946–1954 and/or 1964–1975), Asia and Oceania: anti-colonial nationalism and communism overlapped in the struggle involving the Viet Minh, France, North Vietnam, South Vietnam and the United States. Use this to show that ideology could internationalise a local or colonial conflict during the Cold War.
· Algerian War (1954–1962), Africa and the Middle East: anti-colonial nationalism drove the FLN against French rule. Use this to show ideology as a liberation cause, especially when national self-determination conflicted with imperial claims.

This map shows the changing Republican and Nationalist zones during the Spanish Civil War. It supports analysis of how political and ideological division became territorialised into rival zones of control. Source

Cause category 3: Economic causes

· Economic causes include depression, inequality, resource pressure, imperial markets, financial weakness, or competition for strategic economic assets.
· Economic problems rarely cause war alone; they usually matter because they increase domestic instability, state insecurity, or aggressive foreign policy.
· In essays, make economic causation precise: identify who was affected, how economic pressure changed political choices, and why it contributed to war.

· Spanish Civil War (1936–1939): economic inequality, land hunger and class conflict deepened social polarisation. Use this to argue that economic divisions helped radicalise politics, but the immediate path to war involved military rebellion and political breakdown.
· Chinese Civil War (1927–1937 and/or 1946–1949): rural poverty and peasant grievances gave the Chinese Communist Party opportunities to build support. Use this to show how economic inequality can strengthen revolutionary movements in civil wars.
· Vietnam (1946–1954): colonial economic structures and resentment of French control contributed to anti-colonial resistance. Use this to link economic exploitation with nationalist mobilisation.
· First World War (1914–1918): economic competition and imperial rivalry contributed to long-term tension among great powers, though they were less immediate than the July Crisis. Use this for balanced judgement: economic causes formed part of the background, but political and alliance decisions were more direct.

Cause category 4: Short-term and immediate causes

· Short-term causes are crises, decisions or events close to the outbreak of war that intensified existing tensions.
· Immediate causes are the final triggers, but they are not automatically the most important cause.
· IB essays should avoid “trigger = cause” simplification. A strong answer explains why the trigger mattered only because long-term tensions already existed.

· First World War (1914–1918): the assassination of Franz Ferdinand triggered the July Crisis, but escalation depended on alliance commitments, mobilisation plans, militarism, and Austro-Hungarian and German decisions. Use this to show the difference between immediate trigger and underlying causes.
· Spanish Civil War (1936–1939): the military uprising of July 1936 was the immediate cause, but it followed years of political polarisation, social conflict and fear of revolution or reaction. Use this to argue that the coup triggered war because state authority had already weakened.
· Iran–Iraq War (1980–1988): Iraq’s invasion of Iran in 1980 was the immediate cause, but it rested on territorial rivalry, fear of revolutionary Iran, and Saddam Hussein’s calculation that Iran was weakened. Use this to show how short-term opportunism can activate long-term disputes.
· Falklands/Malvinas War (1982): Argentina’s occupation of the islands triggered war with Britain, but the deeper cause was the unresolved sovereignty dispute and the junta’s domestic political weakness. Use this to connect a precise trigger to both territorial and political causes.

Compact evidence bank: best wars to revise for comparison

· Spanish Civil War (1936–1939), Europe: demonstrates ideological polarisation, political instability, social/economic division, and the slide from domestic crisis into civil war. Best used for essays on ideological causes, civil wars, and short-term versus long-term causes.
· Chinese Civil War (1927–1937 and/or 1946–1949), Asia and Oceania: demonstrates rival political legitimacy, communism versus nationalism, peasant grievances, and the effect of weak central authority. Best used for comparing civil wars with Spain or ideological wars with Vietnam.
· Vietnam (1946–1954 and/or 1964–1975), Asia and Oceania: demonstrates overlap between anti-colonial nationalism, communism, Cold War ideology, and foreign involvement. Best used for essays on ideological causes, nationalism, and how local wars became internationalised.
· Algerian War (1954–1962), Africa and the Middle East: demonstrates anti-colonial nationalism, rejection of French imperial rule, and the political impossibility of compromise. Best used for comparing with Vietnam as another war of decolonisation.
· Iran–Iraq War (1980–1988), Africa and the Middle East: demonstrates territorial disputes, regional power politics, ideological fear after the Iranian Revolution, and leadership miscalculation. Best used for essays on territorial causes or short-term opportunism.
· Falklands/Malvinas War (1982), the Americas: demonstrates a focused territorial dispute intensified by domestic political needs. Best used as a concise comparison with Iran–Iraq or First World War when discussing territory and political calculation.
· First World War (1914–1918), cross-regional but often used in Europe: demonstrates long-term alliances, militarism, imperial rivalry, nationalism, and a clear immediate trigger. Best used for essays on long-term versus short-term causes, but remember the syllabus warning about cross-regional use.
· Second World War (1939–1945), cross-regional: can be used in one regional context, such as Europe or the Pacific, to discuss ideology, expansionism, territorial revisionism, and international crisis. Do not use both regional contexts as separate examples in the same “different regions” answer.

The maps in this category help students visualise how competing claims to rule China became a military struggle for territorial and political control. They are useful for linking ideology, state weakness and geography in civil-war causation. Source

Comparison moves that score well

· Ideological civil wars: compare Spanish Civil War and Chinese Civil War. Both involved ideological polarisation, but Spain’s causes were tightly linked to short-term political breakdown in the 1930s, while China’s conflict was longer and shaped by warlordism, nationalism, communism and Japanese invasion.
· Decolonisation wars: compare Vietnam and Algerian War. Both involved anti-colonial nationalism, but Vietnam became more explicitly internationalised by the Cold War, while Algeria centred more directly on France’s refusal to abandon settler-colonial control.
· Territorial wars: compare Falklands/Malvinas War and Iran–Iraq War. Both involved territory, but the Falklands/Malvinas dispute was geographically limited and politically symbolic, while Iran–Iraq involved regional power, waterways, ideology and fears after revolution.
· Short-term versus long-term: compare First World War with Iran–Iraq War. Both had long-term tensions, but each also depended on short-term decisions by leaders who believed a quick or advantageous war was possible.
· Best judgement pattern: “Although [cause A] was the immediate trigger, [cause B] was more significant because it made compromise unlikely and gave leaders reasons to choose war.”

How to build a high-scoring Paper 2 paragraph

· Start with a direct causal claim: “A major long-term cause of the Spanish Civil War was ideological polarisation, because...”
· Add precise evidence: name the war, dates, groups, leaders, ideology, crisis or dispute.
· Explain causation, not just context: show how the factor increased tension, reduced compromise, mobilised violence or encouraged leaders to choose war.
· Weigh importance: compare it with another cause, such as economic inequality, territorial dispute or short-term trigger.
· Link back to the question using the command term: “Therefore, ideological causes were significant, but they became decisive only when political authority collapsed.”

Broad IB-style question angles

· “To what extent were ideological causes the most important causes of 20th-century wars?” Use Spanish Civil War, Chinese Civil War, Vietnam or Algerian War.
· “Compare and contrast the causes of two wars, each from a different region.” Pair Spanish Civil War with Chinese Civil War, Vietnam with Algerian War, or Falklands/Malvinas War with Iran–Iraq War if regional requirements fit.
· “Evaluate the importance of short-term causes in the outbreak of two wars.” Use First World War, Spanish Civil War, Iran–Iraq War or Falklands/Malvinas War.
· “Discuss the role of territorial causes in the outbreak of war.” Use Falklands/Malvinas War, Iran–Iraq War, or First World War in a defined regional context.
· “Examine economic causes of war.” Use Spanish Civil War, Chinese Civil War, Vietnam, and be careful to explain economic causes as contributing factors rather than sole causes.

Exam traps and common mistakes

· Writing narrative instead of analysis: do not retell the whole war; focus only on why it began.
· Confusing causes with practices or effects: technology, mobilisation and peacemaking belong to other syllabus sections unless directly linked to causation.
· Ignoring short-term versus long-term: always separate background tensions from triggers.
· Using one example too vaguely: “nationalism caused war” is weak unless tied to a named war, group, dispute and date.
· Forgetting regional rules: if asked for two regions, choose examples from two IB regions; do not use Second World War in Europe and Second World War in the Pacific as two different regions in one answer.
· Treating suggested examples as compulsory: the syllabus examples are suggestions, but your essays still need precise, well-revised wars.

Quick judgement sentences to adapt

· Ideology: “Ideology was most significant where it made compromise impossible, as in Spanish Civil War and Chinese Civil War, but it usually worked alongside political instability.”
· Territory: “Territorial disputes caused war most directly when leaders linked land to national prestige or security, as in Falklands/Malvinas and Iran–Iraq.”
· Economics: “Economic grievances were rarely sufficient alone, but they intensified social division and made radical solutions more attractive.”
· Short-term triggers: “Immediate causes explain why war broke out when it did, but long-term causes explain why the crisis became a war rather than a settlement.”
· Comparison: “The key difference is that [War 1] was driven mainly by [cause], whereas [War 2] was driven more by [cause], although both shared [common factor].”