"It is estimated that over 100,000 Confederate and somewhere between 100,000 and 200,000 Union troops accepted Christ during the Civil War--roughly ten percent of the men engaged. There are many accounts of the change that took place in the men, both during the war and afterwards, as a result of the many revivals and movement of the Holy Spirit."
Here is an interesting article that addresses the subject.
http://www.greatamericanhistory.net/revival.htm
Of course, we could not formal religious movements in the military today with all the PC restraints. This was something profound and unique in American history.