Why did Civil war battles have such high casualty rates?

Weapon technology had advanced but the commanders still used old military tactics on the field. Rifles could shoot further and more accurately than in previous wars. Pistols that fired multiple shots and repeating rifles came into use in battle for the first time. Artillery also became more accurate and were more mobile, allowing them to get closer to the enemy. With the advance in weapons, there was little advance in treatment of the wounded. Field hospitals had not been used before the war. Anesthesia and medicines were still not used to any great extent. More soldiers died in battle. The largest killer was disease---not combat. This could be attributed to lack of medical technology, prevention of disease and exposure to elements. Before the war, the civilian population did not travel and mingle with other people or other climates. During the war, people were exposed to diseases that were new to them and to different climates.