I am looking for details of this officers career. I know he was with the 40th Regiment of Foot from at least 1775 but have no knowledge of his career prior to January of that year. He rose to command the light company 1777-80, and the regiment itself 1780-81. He was killed at the storming of Fort Griswold in 1781. At the time of his death he was c29 years old.
I don’t know too much about Major William Montgomery myself, though this resource has a good amount of information about the regiment’s history in the earlier 1700’s, maybe connecting with them, they might have information or be able to direct you more closely to some great stuff.