In 1810, Isaac Brock was transferred to Upper Canada as Major General on the Staff of North America. The growing hostilities between Great Britain and the United States convinced Brock that war was inevitable and that Upper and Lower Canada faced the very real prospect of an American invasion. Despite the lukewarm support he received from the Legislature of Upper Canada, Brock energetically set about the task of preparing for the defence of Canada.
By 1812, he was able to report that 11,000 Canadian militiamen were available. His counterpart in Lower Canada, however, was concerned about the creation of such a large militia. Sir George Prevost was of the opinion that it would be unwise to arm more than 4,000 men due to the apparent dissatisfaction of some of the population with the British administration of Upper and Lower Canada.