The Civil War was the deadliest conflict in American history, killing more American soldiers than World War I and World War II combined. However, most Civil War casualties weren't caused by battle wounds. Instead, about two-thirds of Civil War deaths resulted from disease, according to the Civil War Preservation Trust.

Disease

Disease killed more than 400,000 soldiers in the Civil War, according to the University of Houston's Digital History website. Dysentery was the most common fatal disease, according to the Civil War Preservation Trust. Soldiers also died from typhoid fever, a bacterial disease transmitted by lice, as well as malaria, pneumonia, smallpox and yellow fever. Several factors contributed to the spread of disease, including poor hygiene, spoiled food, impure water, lack of medical knowledge and lack of surgeons.

Battle Wounds

Battle wounds killed about 200,000 soldiers in the Civil War. Most battle deaths were caused by rifle bullets, especially from the percussion rifle, according to Georgia Perimeter College. Infection and gangrene also caused many amputations and casualties.