Militarism, Alliances, Imperialism, Nationalism
M.A.I.N. is a good way to remember the causes of WWI. Militarism was growing in Europe at the time as countries were building up and modernizing their militaries with new technology. Alliances were a cause since countries signed agreements to support each other in the event of conflict. Imperialism was growing as European powers were competing for colonies and resources in Africa and Asia. Nationalism is the last cause because European countries were growing in their national pride and sense of power. These MAIN causes acted as a powder keg that simply needed a spark to ignite.