american civil war casualties are those soldiers, both union and confederate, who died, were wounded, went missing or were captured. the american civil war was the nation's bloodiest war. the violence in battles such as shiloh, antietam, stones river and gettysburg shocked everyone in the country, both north and south. it also shocked international observers. of those who died, by far the leading cause of death was disease. the exact number of dead will never be known with any certainty. all civil war casualty numbers are estimates, no matter what the source. for over a hundred years the total number of dead has been accepted by most historians as 618,222, generally rounded off to 620,000. newer estimates have put the number at about 750,000 or about 20% higher than previously approximated.