Cause of World War I The cause of WWI has been a large debate among historians. The possible causes include imperialism, nationalism, militarism, the assassination of Franz Ferdinand, and the alliances created between the countries which may have tension. In this war, one country or circumstance did not particularly cause the breakout in violence. Political disagreements, economic conflicts, and alliances were other probable causes. I believe the largest and most direct reason for the outbreak of war was the murder of the Austrian-Hungarian Archduke and his wife by the Serbians. Gavrilo Princip was the Serbian who carried out the brutal assassination of the beloved man in power, Franz Ferdinand. Nationalistic ideas as well as militaristic