History· 5 min read

The Causes of World War One (MAIN), Explained

World War One began in 1914, but the pressures had built for decades. A common way to remember the long-term causes is the acronym MAIN.

MAIN: the four long-term causes

Each letter is one underlying cause.

  • Militarism: an arms race and the glorification of military power, especially between Britain and Germany.
  • Alliances: rival blocs (the Triple Alliance and Triple Entente) meant a local war could pull in many countries.
  • Imperialism: competition for colonies and resources created tension between the great powers.
  • Nationalism: intense national pride and independence movements, especially in the Balkans.

The spark

In June 1914, the assassination of Archduke Franz Ferdinand of Austria-Hungary in Sarajevo triggered a chain of ultimatums and alliance commitments that turned a regional crisis into a world war within weeks.

Frequently asked questions

What does MAIN stand for?

Militarism, Alliances, Imperialism, and Nationalism — the four long-term causes of World War One.

What event triggered World War One?

The assassination of Archduke Franz Ferdinand in June 1914, which set off the alliance system.

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