Nationalism, militarism, imperialism, and the system of alliances were four main factors that pressed the great powers towards this explosive war." (Clock Magazine, 1915 Aug. 17). Although Francis Ferdinand's assassination had sparked the beginning of the war, this however was not the main cause. The four major roles that played in the cause of World War I were Nationalism, Militarism, Imperialism, and the Alliance System.
Nationalism: a philosophy that is purely focused on patriotism, loyalty to one's nation and seeing it as the superior nation. In example of a nationalistic cause in the war, Austria-Hungary was getting apprehensive when the Slavs in northern part of their empire wanted to unite with Serbia. Of course, having a strong nationalism in Austria-Hungary, Austria-Hungary started being concerned. They did not want to lose their land and power to Serbia, and sooner or later, this lead to Austria's military preparation in case it ever broke out.
Militarism: a philosophy that bases one's organization purely on the strict ideas of strong military, control over aggression, and mass production of weaponry and any other military supplies. The first conflict started when Germany grew jealous of Great Britain's Navy and their increased naval production. At the time, Britain had the best all-around Navy in Europe, including the dreadnoughts; a ship designed to be superior to any other ever constructed. Threatened by this, Germany started the mass production of weaponry, ships, and any other military means. After doing so, Germany went into competition against Britain and their Navy, and hopefully scare them into submission. .
Imperialism: a philosophy stating that, to create or reform a country into a powerful country, it must take over all means of political, economical and military status of another country through aggression. Europe at this time was very focused on imperialism.