What connotation did "war devil" have?

"Some of the men muttered and looked at the youth in awe-struck ways. It was plain that as he had gone on loading and firing and cursing without the proper intermission, they had found time to regard him. And they now looked upon him as a war devil."

I wold have to say 'great warrior,' or 'fought like the devil.' Its connotation would have been complimentary to say the least.