The deadliest thing that faced the Civil War soldier was disease. For every soldier who died in battle, two died of disease. …
From Wikipedia: ” For 110 years, the numbers stood as gospel: 618,222 men died in the Civil War, 360,222 from the North and 258,000 from the South — by far the greatest toll of any war in American history.”
New data suggests that 650,000 to 850,000 men died as a result of the American Civil War.
That said, two thirds of all deaths in the Civil War were caused by a bug, not a bullet: diarrhea, dysentery, measles, small pox, malaria, pneumonia, or camp itch.