During the
Revolutionary War, Van Cortlandt commanded 4th Battalion of the New York Continental Infantry, served on
George Washington's staff, and commanded the
Continental Army's
2nd New York Regiment. He fought at the
Battle of Saratoga, was with the Army at
Valley Forge, and took part in the
Sullivan Expedition. In his memoir, Van Cortlandt recalled his activities during the 1777 Saratoga campaign. In the course of attempting to capture a British gunboat on the
Hudson River on the night of the September 17, he and his men stumbled upon an advance guard of
Burgoyne's British forces at a place he designated as "Blind Mores". Upon realizing that a main enemy encampment was nearby, Van Cortlandt dispatched messengers to Continental Army commanders in the area, including
Benedict Arnold and
Enoch Poor, and
Daniel Morgan, informing them that "the Enemy was advancing so that they (the Continental Army) might make arrangements Immediately to check their (Burgoyne's troops) advance." Van Cortlandt's regiment occupied a position on the left flank, and played a significant role in the fighting on September 19 and in the subsequent
Battle of Bemis Heights on October 7, which led to Burgoyne's surrender on October 17. After Burgoyne's surrender, Van Cortlandt moved his regiment moved to
Kingston, which Sir
Henry Clinton had burned before his hasty retreat to New York; Van Cortlandt subsequently joined Washington at White Marsh, and then went into winter quarters at
Valley Forge. Van Cortlandt subsequently commanded the post at
Radnor Friends Meetinghouse; his regiment pursued the British during their retreat from Philadelphia, and took part in the June 1778
Battle of Monmouth. He rejoined the regiment in Poughkeepsie, and resumed the command during the winter of 1778 in the cantonments at
New Windsor.
Sullivan Expedition In the summer of 1779, Van Cortlandt's regiment took part in the
Sullivan Expedition. Sullivan's adversary was the Mohawk war chief
Joseph Brant, who combined his forces with those of Loyalist John Butler to attack the frontier settlements of New York and Pennsylvania. Van Cortlandt came to respect Brant's abilities, and hung his portrait at
Van Cortlandt Manor after the war. The immediate task confronting Van Cortlandt was to clear a road from Easton through the Wyoming Territory, a distance of some sixty-five miles. He completed his portion of the road in thirty days. The difficulty of this project was recognized by Sullivan when he thanked Van Cortlandt and Colonel
Oliver Spencer of the
Fifth New Jersey Regiment for their "unparalleled exertions in clearing and repairing the road to Wyoming." In 1779 and 1780, Van Cortlandt was a member of the
Court Martial that charged
Benedict Arnold with improper conduct while in command of
Philadelphia. This was the third time that Van Cortlandt became directly embroiled with
Benedict Arnold. This time, the Pennsylvania Provincial Council had accused Arnold of committing eight violations while supervising the city. A Congressional committee determined that some of the charges should be dismissed, others could only be tried in a civil court, and the remainder were subject to review by a court martial. According to Van Cortlandt's memoir, a minority sought to have Arnold cashiered out of the army; instead, he was merely reprimanded by
George Washington. It is now known that Arnold was guilty of some of the charges relating to
war profiteering, but that a poor case was made against him by the Pennsylvania authorities. Van Cortlandt's correspondence regarding Arnold includes these two passages: I remained time sufficient to discover the Vile conduct of Arnold in procuring a Vast Quantity of goods from the Merchants of Montrial which he intended and which I believe was appropriated to his benefit and also for improper conduct before the Court he would have been arrested himself, but escaped by procuring an order from Genl. Gates to send me the morning after the Court has adjourned, to Schenesborough (Whitehall) by which means the Court was dissolved, Hazen released from arrest, & Arnold escaped Sensure which he ought to have had. Genl Arnold being under arrest for improper conduct in Philadelphia while he commanded there I was one of the court martial. M. G. Howe President and there were also on that court four officers who had been at Ticonderoga when Colo. Hazen was called on for trial as before related and we were for Cashiering Arnold but were overruled and he was sentenced to be reprimanded by the Commander-in-Chief. If all the court had known Arnold's former Conduct as well as myself how he and his Brigade Major had Robbed Merchants in Montreal he would have been Dismissed from serving any longer in our Army for he would have been cashiered if so he would never have had the Command at West Point and Major Andrew might have lived until this day." In the fall of 1780, Van Cortlandt's regiment served as the Army's rear guard as it marched to Yorktown. There he commanded the New York Brigade in the trenches until
Cornwallis surrendered. He then took charge of the British prisoners on their march to Fredericksburg, and finally went into Winter quarters at Pompton, New Jersey. Van Cortlandt was commended for gallantry at Yorktown, and mustered out of the service at the end of the war with the rank of
Brigadier General. ==Later career==