Gugy purchased a commission in the Dutch army before joining a newly formed British regiment, the King's Royal Rifle Corps as a lieutenant in 1756, serving under General James Wolfe at Quebec in 1759.
He remained in Canada, and having been trained for the Engineers and as an accomplished linguist, he was chosen by Sir Frederick Haldimand, who became military governor of Trois-Rivières, Quebec in 1763, to be his secretary.
In 1778, when refugees started arriving from across the border, with the marked approval of the now Governor of Canada, his old friend Sir Frederick Haldimand, Gugy erected dwellings and a school on his seigneuries at Yamachiche, Quebec, to house them.
Towards the end of his life, the owner of a neighbouring fief claimed that Gugy had been responsible for wilful damage to his property during the construction of buildings for the American refugees.
In Sketches of Celebrated Canadians, it was reported that following the verdict, He gently made his way through the crowd, and, going to his lodgings, without speaking one word, entered his room and locked the door.