 But all that was to change when Lee's Army of Northern Virginia started marching north in late June.On June 25, the brigade was assigned as the 3rd Brigade, 3rd Division, I Corps, and ordered to follow the rest of the Army of the Potomac north.The 12th and 15th regiments were detached at Westminster, Maryland, on July 1, to guard supply trains, and the remaining regiments arrived on the battlefield late that evening, and camped to the rear of Cemetery Hill.