The primary causes of conflict in Europe leading to World War I included nationalism, militarism, imperialism, and a complex web of alliances. Nationalistic fervor led competing nations to pursue aggressive policies, while militarism resulted in an arms race among European powers. Countries sought to expand their empires, leading to territorial disputes and tensions over colonies, particularly in Africa and Asia. The assassination of Archduke Franz Ferdinand in 1914 triggered a system of alliances that drew multiple nations into war, illustrating how entangled relationships among countries heightened the likelihood of a large-scale conflict. This lethal combination of factors pushed Europe into World War I.