By John Ostapkovich

PHILADELPHIA (CBS) – It was 149 years ago this weekend that a climactic battle of the Civil war was fought in South Central Pennsylvania. It’s been recounted in many books, but one attacks the subject a little differently.

“Cain at Gettysburg,” by columnist and commentator Ralph Peters, is a historical novel, or maybe novelized history.

His presentation of what officers, from the rank of captain and up, said and did is based on voluminous contemporary writings.

Foot soldiers are fictionalized, to provide boots on the ground perspective through Peters’ own military experience. He says a critical role fell to Irish immigrants from Philadelphia.

“Those troops of the 69th Pennsylvania, the Philadelphia regiment at “The Angle,” they had survived the Irish potato famine, the famine-ships coming to America, the worst the docks of Philadelphia had to offer, and they weren’t drafted. They volunteered to fight for the Union and they fought like Lions,” says Peters.

Peters said the tide turned in part because, for once, Lee’s subordinates wouldn’t do what he told them.