In 1775, Schenck was one of the first residents of Hunterdon County to volunteer to serve as a Minuteman in the months following the Battles of Lexington and Concord. He first served as a lieutenant and then was elected a captain of what was to become a company of the 3rd Regiment Hunterdon Militia. In eight years of service with the Militia, Captain Schenck fought in most of the major battles of the War in New Jersey and Pennsylvania. He was at the battles of Monmouth, Trenton, the Second Battle of Trenton (where he took command of another 3rd Regiment company after its lieutenants deserted and its captain fell sick), Princeton (where a cannonball took away a tree branch he had stooped to pass under), Bound Brook and Germantown.