NEW YORK (AP) — A Civil War history focusing on the Army of the Potamac has won a $5,000 award.

Prize officials announced on Thursday that Steven E. Sodergren's "The Army of the Potomac in the Overland & Petersburg Campaigns" is this year's winner of the William E. Colby Award. The book is set during the conflict's final year, 1865, and tells of the emergence of trench warfare. Sodergren is associate professor of history at Vermont's Norwich University.

Established in 1999, the award is given in partnership with the Chicago-based Pritzker Military Foundation and named for the late CIA director and ambassador. It's presented to a fiction or nonfiction writer for adding to the public's knowledge of "intelligence operations, military history or international affairs."

Previous winners include Dexter Filkins and Karl Marlantes.