World War II was the deadliest conflict in human history. While exact numbers are impossible to calculate, historians estimate that between 70 million and 85 million people died—about 3% of the world's population at the time. Civilians accounted for the majority of these deaths (estimated at 50-55 million) due to famine, disease, massacres, and aerial bombing. The Soviet Union suffered the highest losses, with an estimated 27 million dead, followed by China with 15-20 million. These staggering numbers reshaped global demographics and led to a profound cultural shift in how the world viewed war and human rights.