By 3:30 that afternoon, President James Buchanan ordered a company of U.S. Marines (the only government troops in the immediate area) to march on Harpers Ferry under the command of Brevet Colonel Robert E. Lee, lieutenant colonel of the 2nd U.S. Cavalry Regiment. Lee had been on leave from his regiment, stationed in Texas, when he was hastily called to lead the detachment and had to command it while wearing his civilian clothes.[20]
https://en.wikipedia.org/wiki/John_Brown%27s_raid_on_Harpers_Ferry