Newton was commissioned as a lieutenant in the 1st Regiment of Foot Guards, with the rank of captain in the Army, on 9 November 1692. He served in the wars of King William III, and was wounded at the siege of Namur in 1695. On 13 February 1702 he was appointed major of Sir Richard Temple's newly raised Regiment of Foot, and served in the wars of Queen Anne, being promoted to lieutenant-colonel commanding the regiment on 25 August 1704, brevet colonel on 1 January 1707, and colonel of the regiment on 24 April 1710.