The particular circumstances which have created the most unfortunate embarrassments were my having no orders or directions in relation to Upper Canada (which I had considered as not attached to my command) until my last arrival at this place, and my being detained so long at Boston by direction. If I had been directed to take measures for acting offensively on Niagara and Kingston, with authority such as I now possess, for calling out the militia, we might have been prepared to act on those points as early as General Hull commenced his operations at Detroit; but unfortunately no explicit orders had been received by me in relation to Upper Canada until it was too late even to make an effectual diversion in favor of General Hull. All that I could do was done without any delay.
On August 15, 1812, Secretary of War Eustis is also writing to General Dearborn advising that the President Madison had rejected the armistice.
I am commanded by the President to inform you that there does not appear to him any justifiable cause to vary or desist from the arrangements which are in operation; and I am further commanded to instruct you that from and after the receipt of this letter and allowing a reasonable time in which you will inform Sir George Prevost thereof, you will proceed with the utmost vigor in your operations. How far the plan originally suggested by you of attacking Niagara, Kingston, and Montreal at the same time can be rendered practicable, you can best judge. Presuming that not more than a feint, if that should be deemed expedient, with the troops on Lake Champlain aided by volunteers and militia can be immediately effected against Montreal, and considering the urgency of a diversion in favor of General Hull under the circumstances attending his situation, the President thinks it proper that not a moment should be lost in gaining possession of the British posts at Niagara and Kingston, or at least the former, and proceeding in co-operation with General Hull in securing Upper Canada.
On the same day, General Dearborn also wrote to the Secretary of War,
If the troops are immediately pushed on from the southward, I think we may calculate on being able to possess ourselves of Montreal and Upper Canada before the winter sets in. ... I am pursuing measures with the view of being able to operate with effect against Niagara and Kingston, at the same time that I move toward Lower Canada. If the Governor of Pennsylvania turns out two thousand good militia from the northwesterly frontier of his State, as I have requested him to do, and the quartermaster-general furnishes the means of transportation and camp-equipage in season, I am persuaded we may act with effect on the several points in the month of October at farthest.