The leader of Germany during World War I was Kaiser Wilhelm II. He ruled from 1888 until his abdication in 1918. A prominent figure in German militarism, he initially aligned Germany with Austria-Hungary during the war but later faced criticism for his leadership. His aggressive foreign policies and the nation's military strategies contributed to the outbreak and escalation of the conflict. As the war progressed and Germany began to face significant defeats, popular support for Wilhelm II dwindled. Ultimately, he was forced to step down, leading to the establishment of the Weimar Republic.