Answer:
Militarism denoted a rise in military expenditure, an increase in military and naval forces, more influence of the military men upon the policies of the civilian government, and a preference for force as a solution to problems.
The alliance system caused the World War I to escalate from a regional conflict into a global war. Two major alliances existed in Europe prior to World War I. The Triple Alliance included Germany, Austria-Hungary, and Italy, while the Triple Entente included the Soviet Union, Britain, and France. After the assassination of the Austrian archduke Franz Ferdinand, Austria and Serbia came into conflict. Austria and Serbia were allied with Germany and Russia respectively, leading Germany and Russia to declare war on each other. The conflict then spread across the globe as a complex web of alliances forced more countries into the conflict.
Imperialism was a cause because building an empire needs manpower such as an army and a navy to conquer and keep the land that they colonized.
The most direct way nationalism caused World War 1 was through the assassination of Archduke Franz Ferdinand, who was the heir to the throne of the Austro-Hungarian Empire.
In summary, Militarism brought military into politics more, which heightened tension and people who prophet from war encouraged it. Alliances escalated the conflict from only a few countries to a *World War* because when one country was in the countries the were allied with had to be a part too in order to keep their alliance. Imperialism was the motivation, if you will, for the war. It caused counties to make deals and invade other countries to become more powerful. Nationalism kicked off the war when Archduke Franz Ferdinand was killed for the purpose of creating new order in Austria-Hungary which ended up essentially bringing the nations involved to their boiling point.
