World War I was a complex event with multiple contributing factors. A key cause was the alliance system, where countries pledged to defend each other. This meant that a small conflict could escalate quickly.

Militarism, or the build-up of military strength, also played a role, fostering an environment of suspicion and competition. Imperialism, the desire to expand empires, led to rivalries over colonies and resources.

Finally, nationalism, a strong sense of pride in one's country, sometimes led to aggressive foreign policies and a desire for independence. The assassination of Archduke Franz Ferdinand acted as the spark that ignited these underlying tensions, triggering the war.
