Why did the civil war cost so many lives?

Answer 1

Two primary reasons. Possibly three, depending on how you look at it. Wars have been brutal, basically forever. The idea in a war is to make it so that your enemy can no longer be a threat to you. That is done by killing or seriously injuring your enemy. If you wanted to win, you needed to be able to march in to the headquarters of your enemy and threaten to take the life of the leader if he refused to surrender.
So:

1. The civil war involved a lot of people, so a lot of people were injured and outright killed. 2. The civil war involved some of the newer technology, such as canons, rifles, revolvers and trains to make everything a little more mobile, even though the trains didn't provide the advantage that many had hoped. 3. The newer technologies allowed enemies to inflict injury at a much greater distance. Basically, if you could see your enemy, it was possible (with luck and a good marksman) to kill or injure him. With that much injury going on and little in the way of medical understanding, it was inevitable that people would die from infections. In fact, most civil war deaths were from infection.

Answer 2

More powerful and accurate weapons.

Virtual absence of medical resources.

Confederate stubbornness and refusal to surrender when it was obvious they couldn't win.

Answer 3

New types of cannons and bullets were used.

Answer 4

infections and disease.