[2] As Lieutenant Colonel of the 80th Foot he saw action in the American Revolutionary War,[1] serving under Benedict Arnold in the raid against Richmond.

After repatriation, he was appointed to the board of commission in 1782 to examine claims for compensation to those "who having remained loyal to the mother country, had suffered in their rights, properties and profession."

After the outbreak of the French Revolutionary Wars, he served in the West Indies, commanding the 2nd Brigade under Charles Grey in Barbados in 1794.

[1] After accepting the French surrender on 20 April, he was made Governor of Guadeloupe, but died on 3 June of yellow fever and was buried in the primary bastion of Fort Maltilde.

[1] When the French later regained possession of the island Victor Hugues issued a declaration on 10 December, which stated "That the body of Thomas Dundas, interred in Guadeloupe, shall be taken up and given as prey to the birds of the air.