Causes of World War One: imperial rivalry, militarism, the alliance system and the July Crisis for O-Level Elective History

Why this module matters

The First World War (1914 to 1918) reshaped the twentieth century, and understanding why it broke out is the foundation for everything that follows in O-Level Elective History, from the Treaty of Versailles to the rise of authoritarian regimes. The skill this module trains is the most important one in the whole course: distinguishing long-term causes that built up tension over years from the short-term trigger that set war off, and then explaining how the two combined.

This guide ties together the module's dot points, each with its own worked detail and practice. See the subject hub at /sg-o-level/history and the full syllabus list at /sg-o-level/history/syllabus.

The long-term causes

By 1914 Europe was already a dangerous place, and three deep-seated rivalries explain why.

• Imperial and colonial rivalry. The great powers competed for colonies, markets and prestige, and this competition spilled over into crises such as the Moroccan crises and the collapse of Ottoman power in the Balkans, where nationalism made the region a powder keg. Work through the detail at imperial and colonial rivalry.
• Militarism and the arms race. Armies grew, the Anglo-German naval race accelerated, and generals and rigid war plans gained influence, so that mobilisation timetables shaped what governments could do. See militarism and the arms race.
• The alliance system. The Triple Alliance and the Triple Entente divided Europe into two armed camps, so a quarrel between two states risked dragging in their allies. Study the alliance system and rival blocs.

The short-term trigger: the July Crisis

The deep tensions did not have to lead to war in 1914, but the assassination of Archduke Franz Ferdinand at Sarajevo on 28 June 1914 set off a five-week chain reaction. Austria-Hungary issued a harsh ultimatum to Serbia, encouraged by Germany's "blank cheque" of support; Russia mobilised to protect Serbia; and the rigid war plans, above all the Schlieffen Plan, turned mobilisation into invasion. Trace the sequence at the July Crisis and outbreak of war.

How long-term and short-term causes combine

The examiner's favourite question is essentially "what mattered more, the underlying tensions or the spark?" The best response refuses a simple answer: the assassination only led to a general war because the long-term causes had already created two armed, suspicious blocs with rigid plans. Remove the alliance system or the war plans, and Sarajevo might have stayed a local crisis. This is the cause-and-consequence reasoning that the "How far do you agree" structured essays reward throughout the course.

Check your knowledge

Try these under timed conditions, then test yourself with the module quiz.

1. State two long-term causes of the First World War. (2 marks)
2. Explain the difference between a long-term cause and a trigger. (2 marks)
3. Explain why the alliance system helped turn a local crisis into a general war. (3 marks)
4. State what is meant by Germany's "blank cheque" to Austria-Hungary. (2 marks)
5. Explain why rigid war plans such as the Schlieffen Plan made the July Crisis more dangerous. (3 marks)