WWI (1914–1918) vs WWII (1939–1945) World War I introduced industrialized death to a global scale. Trenches, artillery, and mass mobilization pulled entire societies into conflict. Yet most casualties were still soldiers, and the violence, while unprecedented, followed the front lines. World War II erased that boundary. The figures in this reel reveal a shift in how wars were fought and who paid the price. In WWI, the highest death tolls were concentrated in empires fighting each other head-on: