World War I was a global war centered in Europe that began in 1914 and lasted until 1918. It involved over 30 countries and resulted in over 15 million deaths. The war started due to increasing nationalism, imperialism, militarism, and a system of alliances that drew the major European powers into war. The immediate trigger was the assassination of Archduke Franz Ferdinand of Austria-Hungary by Serbian nationalists. The war was fought mainly in trenches along the Western Front and resulted in new weapons and military technology but little movement in the frontlines, leading to mass casualties. The war had far-reaching political, cultural, economic, and social impact.