Sharp's Eagle by Bernard Cornwall

The first published book of Bernard Cornwall's Richard Sharp series. It's a series about a super salty British army officer as he fights through Flanders, Portugal and Spain during the Napoleonic Wars. He was kind of skeptical about Sean Bean playing sharp at first because he didn't have black hair andSharp in the books does have black hair. But Cornwall came to like Bean's performance so much that he made sharp. Like he made him like grow up in Yorkshire so that he would match Sean Bean's accent. In later books, he just kind of stopped mentioning Sharps hair color at all.