The same day Meigs arrived back home, he joined Hunt's Light Company M, 2nd United States Artillery, newly reconstituted and now a reserve unit attached to General Irvin McDowell Army of Northeastern Virginia. The following day, McDowell assigned Company M to Colonel Israel B. Richardson 4th Brigade, Second Michigan Volunteers. Sources vary as to what John Meigs' official role was. Several, including the official U.S. Army biographical register, claim he was an aide-de-camp to Colonel Richardson. However, others note that he was formally assigned to Major Hunt's Light Company M. Among these are the Meigs' family, and Meigs himself. It is clear, however, that he carried orders and acted as an observer for Hunt and carried orders for Richardson.