For the average artillery piece it took eight highly trained artillerymen to form a gun crew. Each member of the crew was cross-trained to do all the jobs required to operate a gun. If a crew member was killed or wounded, another member of the crew could take his place. Gun crews were among the best trained soldiers in either the Confederate or Union armies. They were also vulnerable. They had to see their target to hit it. If they could see their target, the enemy soldiers they were targeting could see them. 