Nationalism, imperialism, militarism, and rival alliances in Europe led to increased tensions between countries. The assassination of Archduke Ferdinand triggered a series of events that started World War I. Germany launched the Schlieffen Plan to quickly defeat France but trench warfare ensued. The US later joined the Allies and helped achieve victory. The devastating effects of the war ended several empires. The resulting Treaty of Versailles and League of Nations aimed to establish peace but their terms deeply punished Germany.