Tensions in Europe before WW! were most increased by what?

Tensions in Europe before World War I were primarily increased by a complex web of alliances, militarism, nationalism, and Imperialism. The assassination of Archduke Franz Ferdinand in 1914 acted as a trigger, leading to Austria-Hungary's declaration of war on Serbia, which activated various alliances. Countries were vying for power and territory, and the arms race further intensified these rivalries. Nationalistic fervor and colonial competition also contributed to the volatile atmosphere, setting the stage for a large-scale conflict.