…was at the hands of an American Indian confederation in the Midwest, the (original) Battle of the Wabash (River), near present Ft. Wayne, Indiana(!). Seems the Revolutionary War didn’t end there with the 1783 Treaty of Paris, which amounted to little more than a ‘separate peace’ between His Majesty King George III on the one hand, and the United States of America on the other. Hostilities continued between Old Northwest Natives and their Native allies on the one hand, former allies of The Crown, and illegally encroaching U.S. settlers on the other, unrestrained by the U.S. government (as usual). What the Wikipedia article leaves out is that British forces took a few years to evacuate the Midwest, leading the Indians to believe they might rejoin the struggle – and to feel betrayed and abandoned by their Britannic ally when they didn’t. In addition, the Lenape of this war were the first Native Nation the new U.S. had signed a Treaty with (ceding it most of central Pennsylvania), and had been promised a seat in the Continental Congress as well as a Lenape-led Indian state in what became instead the Settler state of Ohio. (Cf. Delaware County, Ohio.)
Long story short, although the Paris Treaty transferred Britain’s claims over the Old Northwest to the U.S., the US still had to “treat with” the Native Nation-occupants before exploiting any part of the territory itself or on behalf of its Settler-people. This the US failed to do. In fact, President George Washington, other “Founding Fathers,” and many other settlers had long improperly speculated on land in the Ohio Country, back to the French and Indian War as a result of which its claims transferred from France to Britain … and Washington’s home-colony of Virginia (then including West Virginia) even long claimed Ohio as part of its territory. King George had tried to put a stop to all this illegality with his Proclamation of 1763,* setting colonial boundaries at the top of the Appalachian Mountains and restricting settlement to the West, but was unable to police it in such a remote area against his own settlers. Many Native Nations were acquainted with Britain’s Sovereigns and their ostensible rule over their settlers and colonies, and again, felt betrayed when the settlers got other ideas, with impunity. Thus the colonists, especially their Planter elites (the future Founding Fathers), sowed the seeds of continuing conflict with Sovereign Indian Nations west of the Eastern Seaboard – just as many of their encroachments on the coast were also at first illegal, only justified by Treaty after the fact. Is it any wonder that they were (are!) said to “speak with a forked tongue”?
(*–I can’t find a comprehensive online treatment of the Proc. of 1763, ie, that isn’t narrowly-focused on U.S. or Canadian interests. However, there were and are many more Indian Reserves in eastern and central Canada — Ontario and eastward — than in the U.S. east of the Mississippi, in part because the British Crown continued to ‘honour’ this Proclamation somewhat, whereas the U.S. assimilated, denied, or “removed” west the overwhelming majority of its eastern Indians. OTOH, Founder speculation and Settler western ambitions, along with Crown resistance to them and attempts to protect the legal rights and territories of the Natives sort-of under his protection, were a significant cause of the U.S. Revolution in the first place — a cause little-emphasized in standard U.S. histories and school systems.)