had been commissioned a captain in the 34th Foot in June of 1744 and promoted again to a major in February of 1747, and later he was made a lieutenant-colonel of the 47th Foot.

In 1753 Monckton was assigned to Nova Scotia, as the second in command under Governor Hopson. Hopson took sick and returned to England and was replaced with Charles Lawrence. In April, 1755 the Governors of the English colonies met and felt that the French were going to attack , even though both countries were at peace. Two thousand troops were mustered in Boston and sent to Monckton to take control of the French Fort Beauséjour in Acadia. On June 16th, 1755, the French surrendered Fort Beauséjour and it was renamed by Monckton as Fort Cumberland. This start the conflict know as the "Seven Years War". After the fall of Fort Beauséjour, Governor Lawrence decided to have Monckton take care of the French Acadians for good. The Acadians would not swear their allegiance to the King of England and not to take up arms against the English. Lawrence, operating out of Halifax, instructed Monckton to break off a number of his troops and send them under one of his brigadiers under Winslow to another part of Acadia, Grand Pré. He ordered ships up from Boston and the Acadians were to be gathered together at several points, loaded into the ships and sent away; to be dispersed amongst the English colonists. Their homes and possessions were to be put to be burnt to the ground.

During the winter of 1758/59 Monckton was in New York perfecting the plans for the assault against Quebec. Monckton was to assumed command of the city after it's fall. In 1761, he was promoted major-general and was to become the governor and commander-in-chief in the province of New York. He organized the attack on the French islands in the Caribbean, which included Martinique. In 1763, the Seven Years War was formally brought to an end with the signing of the Treaty Of Paris, and he returned to England. Monckton died in 1782 and is buried in London.