While I'm primarily struggling with dates of enlistment and discharge for John Jay Jackson because I want to determine exactly when he married Sarah Howard Ijams, apparently John Jackson was pursuing verification of those dates for a very different reason.
As we've already seen, when John Jackson enlisted under Captain John Morris in 1814, he had agreed to five years of service. Apparently, there was a payoff for keeping one's word in the terms of service under which he enlisted. And it didn't seem to be simply how much his survivor's pension might be, once he needed the money. There seems to be a matter of land involved, as well.
As is often the case, when it comes to agreements with the government, there might have been some fine print in the mix. Being that one of farmer John Jackson's sons eventually became an attorney in nearby New Lexington, Ohio, John was apparently well-equipped to take on any arguments arising from having taken advantage of one particular loophole, once it came time for him to call in those governmental promises.
My first clue that something was unusual about the Jackson pension papers was gleaned from a hand-written note affixed to the back of a letter. It contained the explanation:
A Certificate must be produced [?] from a [Commissioned] Officer in service, stateing [sic] the name of your [substitute?] & that he engaged to serve for 5 years from the date of your discharge, as the evidence cannot be procured from the rolls....
Looking further, the pension file revealed the information John Jackson must have been seeking: the document showing one Michael Kelly, "born in Dublin in the Kingdom of Ireland," who had voluntarily enlisted in the army at Bellefontaine in the Territory of Missouri. The document was dated April 13, 1818, and was witnessed by J. J. Jackson.
For his enlistment, Michael Kelly received from Captain McIntosh a twelve dollar bounty, for which he signed by placing his mark. Duly noted, below that, was the Captain's statement explaining the nature of the transaction:
I certify on Honor that the above named Michael Kelley substituted in the place of Quarter Master Sergt John J. Jackson U.S. Rifle Regt.
Penciled in, beneath the signatures, was the question, "Did Kelly engage for 5 years," likely a follow up to the subsequent application made by John Jackson for his pension—or, possibly, for paperwork requesting an enlistment bounty of 160 acres of land.
Substitutions were apparently a permissible way to disengage from that five year term of service. If that transaction was dated April 13, 1818, we might then be able to deduce the reason for John Jackson's desire to end his military service—and also the possible date for the upcoming event motivating his change of plans. If, that is, John Jackson's marriage occurred after the end of his military service.
Above: "Spring. High Water," painting by classical Russian landscape artist Isaac Ilyich Levitan; courtesy Wikipedia; in the public domain.