He then joined the staff of Major General Fitz John Porter as a Lieutenant Colonel and Assistant Adjutant General, and eventually became the Chief of Staff for the Army of the Potomac's V Corps. He was brevetted Brigadier General, US Volunteers on April 1, 1865 for gallant and meritorious services at the Battle of Five Forks, Virginia. Locke: Residence was not listed; 34 years old. Enlisted on 4/19/1861 at New York City, NY as a Adjutant. On 5/2/1861 he was commissioned into Field & Staff NY 12th Infantry He was Mustered Out on 8/5/1861 at New York, NY (Subsequent service in US Volunteers) He was listed as: Detailed 7/14/1861 8th Brigade, Martinsburg, VA Detailed Brgd Major & Asst Adjutant Gnl Frederick Thomas Locke: Residence was not listed; 35 years old.
Enlisted on 9/2/1861 as a Captain. On 9/2/1861 he was commissioned into US Volunteers Adjutant Genl Dept He was Mustered Out on 9/19/1865 Promotions: Capt 9/2/1861 (Captain & Asst Adjutant General) Lt Colonel 8/20/1862 (Lieut Colonel & Asst Adjutant General) Colonel 8/1/1864 by Brevet Brig-General 4/1/1865 by Brevet (Five Forks, VA).