In September 1862, the regiment was assigned to the defenses of Washington, DC as part of Wyndham's Cavalry Brigade. This corresponds closely to the time Colonel De Forest was relieved of command of the regiment. Lieutenant Colonel Johnstone is listed as taking command of the regiment on September 10, 1862. Major Washington Wheeler, who had received his commission as major in July, resigned on September 26. Captain Hammond replaced Wheeler, receiving his commission as major on October 10 effective September 26.