"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.
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.