Aaron died while serving in the War of 1812. He was buried 7/16/1813 in the Military Cemetery, Sacket's Harbor, NY (Post Madison). Aaron was a teacher before the war. He had the rank of Orderly Sergeant. (Londonderry Stewarts - genealogy of).

Related document: Document from National Archives "Records of men enlisted in the U.S. Army prior to the peace establishment, May 17, 1815. Entry for Aaron Stewart, rank Sgt., 21st U.S. Regiment, Capt. Grafton's Company. Enlisted Jan. 15, 1813 for duration of war. Died July 16, 1813. Died at Sackets Harbor, N.Y. July 16, 1813.

Aaron, the eldest son of Captain Stewart, born at Bennington, Vt., March 22, 1775, was named after his uncle Aaron Hubbell, but did not use the "Hubbell" in his signature; sometimes in boyhood he wrote his name "Aron." He was a man of fine physique, standing six feet in his stockings and weighing 190 pounds when only sixteen, was well educated and his penmanship was beautiful. He had many social gifts and was everywhere a favorite. Down to the outbreak of the Second War with England he was engaged in teaching at various places, Charleston, N.Y., Longmeadow, Mass., Rutland, Vt., etc. He married at New Haven Vt., May 16, 1807, Selinda Colt.
Aaron Stewart volunteered in the War of 1812, but his career was brief, and on July 16, 1813, was laid at rest in the Military Cemetery at Sacket Harbor, N.Y., known as "Post Madison."
Aaron was at both the attack on York (Toronto) and the attack on Fort George. The attack on York occurred the day before the battle at Sackets Harbor, so it appears somewhat unlikely that Aaron was at the Sackets Harbor battle. In any event he survived both. The last communication we have from him is his letter dated June 7, and he died on July 16th. My research indicates little activity by the 21st Infantry Regiment between these two dates. I conclude it is likely that Aaron died from disease. I quote: "There was much disease and great loss of life in the lake camps that summer, producing, as can be well imagined, great weakness and demoralization. The surgeon's reports show the prevalent diseases to have been diarrhoea (sic), dysentery, typhus, rheumatism, jaundice, "lake fever," and ergotism. They ascribed as the main causes bad water and poor food. It may be seen, however, that most of these were preventable diseases. Their causes may be traced to general ignorance and neglect of the principles of sanitation, and the mortality largely to ignorance of the proper methods of treatment. Under the then existing conditions the army's food consisted mainly of bread and salt meat, a diet, in itself, conducive to disease. Our men were beset by conditions that are at the present day unknown and unbelievable. Ergotism is a poisoning derived from ergot in the grain, some heads of which, instead of developing into normal kernels, are filled with a black fungus commonly called "smut." Its symptoms are nervous disorders, a gangrenous affection of the extremities, and dementia. Its source was bread made from grain containing this fungus and, as whiskey was then issued as part of the ration, the same contaminated grain being used for distilling, the poison found a second vehicle for entrance into the systems of its victims. What "lake fever" was is not known, but a guess may be hazarded that it would now be called typhoid fever. In those days bleeding was nearly always resorted to in fever cases, and the surgeons reported that the "lake fever" patients usually died under such treatment. There can be little wonder that such should have been the result under the system then in vogue of freely bleeding and depriving the sufferer of all drinking water. Even the lay mind now stands aghast at such monumental ignorance, but it must be remembered that the present generation has witnessed the final passing of this atrocity.
Nothing further of importance occurred on the Niagara during the summer, although the British were aggressive, and picket fights and skirmishes were continually occurring. " (Hampton, Celwyn E. History of the Twenty-first U.S. Infantry from 1812 to 1863. Columbus, Ohio : Edward T. Miller Co., 1911 (borrowed from Armstrong State College Library, Savannah, Ga.) Aaron's statements that he had not yet received a uniform or pay support the argument that the troops were not well-provided for, probably also including food and conditions in general.

From The Stewart Clan Magazine, April 1923: He volunteered in the war of 1812 but his career was brief he was killed at the battle of Sackett Harbor and was buried July 16 1813 in the military cemetery there His widow removed soon afterward from New Haven to Fayston...
This is the only evidence I have seen that claims Aaron died in action (editor)

Correspondence from Stephen R. Wallace, Acting Site Manager, Sacket Harbor Battlefield, Sackets Harbor, N.Y., June 17, 2001, detailing the activities of the 21st Regiment around the time of the battle:
"A total of 298 men of the 9th and 21st Regiments were involved in the battle, and although it is not possible to determine whether Aaron saw action during the battle, his letters home do indicate he saw action, particularly in the York and Fort George engagements. Aaron was involved with a detachment of prisoners, apparently delivered to Greenbush after June 16, 1813. Mr. Wallace suggests examining the Company Book, which should be found in the National Archives, Records Group 98. An inquiry to the National Archives for this did not answer any questions about Aaron's fate. Mr. Wallace suggests he may have succumbed to disease, quite possible as the medical conditions at the time around Sackets Harbor were very poor."