The Hundred Days was Napoleon Bonaparte's final military campaign in 1815. Hundred Days may also refer to: Hundred Days Offensive, the final Allied offensive on the Western Front during the World War I Hundred Days' Reform, a period of social and institutional reform in late imperial China Hundred Days Men, a Union military recruitment initiative during the American Civil War Canada's Hundred Days, the last 96 days of World War I "The First Hundred Days", the start of U.S. President Franklin D.