Ambrose arrived in America as a private in Cpt. I. Hamilton’s Coy. He was listed as being on command on the 27 October 1767 muster. Likely, he was among the detachment sent to Ft. Pitt under Cpt. Edmonstone. He was transferred to Edmonstone’s Coy on 24 June 1768, most likely at Ft. Pitt. Ambrose remained at Ft. Pitt for the next four years until that post was abandoned in the fall of 1772.
When he returned to Philadelphia in the fall of 1772, he remained with Edmonstone’s Coy. He didn’t leave that company until the regiment was reorganized prior to leaving Philadelphia. At that time, Ambrose was transferred to Cpt. R. Hamilton’s Coy on 9 October 1774. He travelled to Boston with Hamilton’s Coy and remained with that company until Christmas. On 25 December 1775, he was transferred to the Grenadier Coy probably in response to the impact of spotted fever on the Grenadiers.
While in Boston, Ambrose stayed out of trouble. He most likely fought at both Concord and Bunker Hill. He was listed as being on duty when the company was mustered at Charles Town Heights on 7 October 1775 and was drafted into the Grenadier Coy of the 52nd Foot in December 1775. He was evacuated to Halifax in March 1776 with the rest of the Army in Boston at that time.
Ambrose remained with the 52nd Foot throughout its American Service. He was present at Staten Island in July 1776 for the beginning of the Long Island Campaign. He was listed as present at Brunswick, New Jersey in April 1777 and at Philadelphia on 9 February 1778 meaning he survived the Philadelphia Campaign and fighting at Brandywine and Germantown. He is last listed as present on 21 September 1778 at King’s Bridge, New York, directly before the 52nd was sent to the West Indies. So he most likely also fought at Monmouth Court House. Unfortunately, his record ends there. He does not appear on the August 1780 or the 1784 rolls of the 52nd Foot. The intervening returns being lost. His fate is unclear; he may have died in battle or of disease in the West Indies. It is also possible he deserted, but not probably as his record indicates he was a model soldier.