Scherb was a cadet in the Infantry Regiment Anhalt on 20 October 1766 and lieutenant on 16 October 1768. In 1769, Scherb served in military during the French conquest of Corsica. He was promoted to lieutenant on 14 January 1777, and to captain on 16 September 1778. As lieutenant colonel, he commanded a battalion of grenadiers under General Adam Philippe Custine on 20 October 1792. As adjutant general, he was brigade leader on 8 March 1793. He was wounded in his right foot by shrapnel and a shot broke his left leg, and subsequently served at the headquarters in Mainz in 1793. He also commanded the second column of the Mainz garrison on 22 July 1793; subsequently he commanded the garrison at Brest on 17 August 1793.