From History of the Late War in the Western Country:
At the close of the American revolution, many persons in England entertained an opinion that the American colonies were not irretrievably lost to the mother country. They hoped that Great Britain would be able, at some favor able moment, to regain the sovereignty of these States; and in this hope it is highly probable the British ministry participated.
From calculations and sentiments like these, as well as from the irritation caused by the failure of their arms,
may have proceeded their unjustifiable conduct on the interior frontiers of the new States. The military posts of Niagara, Detroit, and Mackinaw were detained under various pretences, for many years, in violation of the treaty of peace.
The Indian tribes on our borders were at the same time supplied with munitions of war, and instigated to commit depredations and hostilities on the frontiers of Kentucky, and the settlements northwest of the Ohio.
Although this interference with the Indians was not an obvious and ostensible cause of the war, yet it may fairly be considered as a very efficient cause. Much of that resentment against the British, which prevailed so strongly in the western States, the principal advocates for the war, may fairly be attributed to this source.