De Peyster was educated in London and after returning to
British America, received a commission as an
ensign in the
British Army in 1755. He joined the
50th Regiment of Foot, which had been raised in America in 1748 by
William Shirley, the
Governor of the Province of Massachusetts Bay. In 1745, Shirley, along with De Peyster's uncle, Colonel
Peter Schuyler, had directed the
Siege of Louisbourg against the French in today’s Nova Scotia. De Peyster next held a commission in the
51st Foot, a regiment raised by Lieutenant General
Robert Napier in America, which at one point, had three
Schuylers in it. In 1779, Major De Peyster took over as commandant of
Fort Detroit. In November 1783, De Peyster was promoted to Lieutenant-Colonel of the 8th Foot and transferred to
Fort Niagara, situated at the mouth of the
Niagara River.
Later life He retired in 1794 due to illness, and sold his lieutenant-colonelcy to an associate of
John Fane, 10th Earl of Westmorland, the then
Lord Lieutenant of Ireland. Ten years later, De Peyster had still not been paid. Upon his retirement, DePeyster and his wife moved to
Dumfries, where they settled down at Mavis Grove, a country estate. In 1795, when England was threatened by
Napoleon, he became actively involved with the militia. He played a significant role in enlisting and drilling the 1st Regiment of Dumfries Volunteers. One of the original members of the Volunteers was
Robert Burns, the prominent Scottish poet, who dedicated to De Peyster his "Poem on Life," and with De Peyster carried on a poetical controversy in the columns of the Dumfries
Journal. De Peyster, also wrote poetry and published
Miscellanies, by an Officer in 1813. ==Personal life==