Rebel by Bernard Cornwell

Rebel (The Starbuck Chronicles #1) - Nate Starbuck, of Boston, Massachusetts, has run away from his fanatic preacher father.  He is in Richmond, Virginia right after the 1^st battle of the US Civil War, Fort Sumter.  Being a northerner he is close to being tarred and feathered when he is rescued by his friend’s father, Washington Faulconer.  Faulconer is raising his own militia, Faulconer’s Legion, and Nate, not wanting to return home, joins him.  Thaddeus Bird, Faulconer’s brother-in-law, becomes the colonel that Nate fights under and Thomas Truslow becomes 2^nd Lieutenant Starbuck’s Sergeant.