After several weeks of hard and perilous service, Col. Van Courtlandt with his regiment, was ordered to Albany and thence to the relief of Fort Stanwix, then besieged by Colonel St. Leger with a party of Indians; but on information that the enemy had retired, he joined General Poor, then on the advance to Stillwater, to whose brigade the regiment became attached, and thus made a part of General Arnold's command, forming a portion of the left wing in the first battle of Stillwater, which was fought on the 19th of September. The loss of killed and wounded of the Second New York was two out of eleven, which was a larger proportion than of any other regiment engaged, the next largest being that of Col. Cilley's First New Hampshire, which was one out of seven, all of General Poor's Brigade.[4] At the second battle, which occurred on the 7th of October, the regiment sustained its reputation for determined bravery and hard fighting, and thus bore an honorable part in the most important engagement, thus far, of the war, the results of which changed the whole aspect of the American cause. After the battle of Stillwater, which compelled the surrender of Burgoyne, and rendered fruitless the previous successes of the enemy along the Hudson, the regiment returned to Fishkill, and soon joined the army under Washington, then confronted by the British forces under General Howe, in the vicinity of Philadelphia. It shared the privations and sufferings of the terrible winter encampment at Valley Forge, (1777-8) the march to which of the half naked, half-starved, shoeless army might be tracked in blood through the December snows. It appears from an orderly book[5] found among the papers of Colonel, afterwards Gen. Henry Dearborn, also in the Sullivan expedition, that at Valley Forge, Hardenbergh was Lieutenant and Adjutant of his regiment and often served as Adjutant of the Day at Head Quarters. The whole encampment consisted of about eleven thousand troops; and when it was broken up the following Spring, upwards of three thousand men unfit for duty were left behind, under charge of Colonel Van Courtlandt, while his regiment proceeded with the main army, and participated in the battle of Monmouth, June 28, 1778, winning commendation for bravery and good behavior in that hotly contested engagement.