In 1855, 14th president Franklin Pierce appointed him colonel of the new 2nd U.S. Cavalry (the unit that preceded the modern 5th U.S.), a new regiment, which he organized, his lieut.-colonel being Robert E. Lee, and his majors were Hardee and Thomas. On August 19, 1856, Gen. Persifor Smith, at the request of Kansas Territorial Governor Wilson Shannon, sent Col. Johnston with 1300 men composed of the 2d Cavalry Dragoons from Fort Riley, a battalion of the 6th Infantry and Capt. Howe's artillery company from Jefferson Barracks, near St. Louis to protect the territorial capital at Lecompton from an imminent attack by James Henry Lane and his abolitionist "Army of the North."