In 1860, no one expected any armed conflict would come from the Southern states secession from the Union. Or, if it did, it would be brief and mostly for show purposes. Southerners did not believe the North would mobilize an army against them. The U.S. Senator from South Carolina made the statement he would drink all the blood shed over the South declaring their independence from the Union. Then, as it became apparent that it would become a military confrontation, both sides believed it would not last very long. In 1861, when the Union Army entered the First Battle of Bull Run, they thought a quick victory would bring an end to the war. After the Union loss at Bull Run, the Confederates thought the Union would simply give up the idea re-uniting the North and South. Both were wrong.
During the 1850s there were a number of improvements in weapons, especially rifles. During the Civil War, both armies were equipped with rifles that could shoot farther, could reload faster and were much more accurate than the muskets used in the Mexican–American War. Yet the same military tactics were being used as the earlier war; close formations of men firing in volleys. The new rifles combined with obsolete tactics were responsible for up to 90% of all deaths in battle.
Death was only one of several ways a soldier could be listed as a casualty. During the Civil War a casualty was any soldier who could not perform his duties. This could be for any reason including being sick, wounded, captured, missing or killed. A single soldier could be listed as a casualty several times during the war.
The mid-nineteenth century attitudes towards death and dying for a noble cause were considerably different than modern thinking. Men saw going to war as a chance for glory and honor. They thought that giving one's life for their country or cause was the highest calling. But dying of disease was considered a horrible way to die and most feared it more than dying in battle. War was presented to soldiers as a way to die "for God and country". It represented both Christian and nationalist reasons for going to war. As most were Christians, they were far better prepared to die than to kill. American society in general, and soldiers in particular, believed in the "ars moriendi" (the art of dying) or the "good death." These attitudes left soldiers to believe that a good death was glorious and at the same time a last act of redemption. Also, by dying well a person showed others how to die well.
Another factor which contributed to the high death tolls was the status of medical care at the beginning of the Civil War. In 1861, medical knowledge, diagnostic procedures, equipment, and treatment protocols were very crude by modern standards. Because doctors were often unaware of what caused the diseases they were encountering, and because medical hygiene practices were poor compared with those practiced today, physicians often could do very little to treat their patients; in many cases, they even hastened soldiers' deaths by failing to wash their hands and instruments before moving from one patient to the next - simple protocols which did not begin to take hold until later in the war through the pioneering military medical management efforts of William A. Hammond and Jonathan Letterman. As a result, at times, a physician's treatment of wounds, infections and diseases did more harm than good.
In addition, camp hygiene was extremely poor. Inadequate sanitation facilities, and the lack of shelter, clothing, shoes and food, as well as contaminated water contributed to high death rates in the camps. Diarrhea and dysentery became the leading causes of death with casualty figures showing that roughly twice as many soldiers died from disease as from the most frequent type of battle injury - the gunshot wound (shown in Latin terminology on military medical records as "Vulnus Sclopet").
Other ailments which affected Civil War soldiers included:
Soldiers who were captured by the enemy and held as prisoners of war (POWs) were, in a significant number of instances, housed in such miserable conditions that they faced a higher likelihood of contracting and succumbing to one of the medical conditions shown above; starvation also became a problem in POW camps as more soldiers were captured in battle and food shortages widened.
Even healthcare practitioners were not immune; nurses were particularly at risk of catching diseases from the soldiers they tended.
As many as half of the men killed in battle were not identified when they were buried. The records kept by each company were designed to keep track of how many men were in each unit, not to keep track of each soldier. Confederate military records are much fewer than Union records. When Richmond fell in 1865, records were destroyed, shipped south or left behind. Some of the records were kept by the Union Army and sent to the War Department in Washington, D.C.. The Adjutant General started a bureau for the “collection, safekeeping, and publication of Rebel Archives” in July of 1865. In 1903, the Secretary of War made an appeal to Southern Governors to lend the War Department any Confederate Army records in their possession so they could be copied.
Since about 1900, historians have quoted the numbers produced by Thomas L. Livermore of 618,222 Confederate and Union deaths during the war. Livermore's number was based on incomplete battle reports. It also made a crude guess as to how many died from disease and other causes. His book was titled "Numbers and Losses in the Civil War in America, 1861-65."
Before Livermore, another Civil War veteran, William F. Fox, compiled his estimate the hard way. He went over every muster list, battlefield record and pension record he could find. In 1889 he wrote "Regimental Losses in the American Civil War, 1861-1865". Fox came up with the round number of 94,000 dead. In addition to the number, Fox contributed information on the average Union soldier. For example, that he averaged 5 feet 8 ¼ inches tall and weighed 143 ½ pounds.
Interestingly, before Fox or Livermore, the superintendent of the1870 United States Census, Francis A. Walker, had estimated the number of male deaths to be “not less than 850,000.” But this was not as widely accepted as the lower numbers. Probably the main reason was that the census itself that year was suspected of being wrong. Walker's estimate was based on calculating a typical growth in population which had been consistent during the nineteenth century, minus the number of males who were missing from the census.
Many historians are beginning to accept that the earlier death estimates were probably far too low. A demographic historian from New York's Binghamton University, J. David Hacker, has made a new calculation of Civil War deaths which is about 20% higher. The new estimate is 750,000 deaths and is based on digitized nineteenth century census data. The population of the United States in 1860 was just under 31.5 million. Approximately 2,000,000 men served in the Union forces while about 750,000 served in the Confederacy. About 75% of soldiers were born in America. Of the remaining 25% who were foreign born, many did not appear in any census records prior to the Civil War.