Invasions of Upper and Lower Canada, 1812[]
Map showing the northern theatre of the War of 1812American leaders assumed that Canada could be easily overrun. Former President Jefferson optimistically referred to the conquest of Canada as "a matter of marching." Many Loyalist Americans had migrated to Upper Canada after the Revolutionary War, and the US assumed they would favor the American cause, but they did not. In prewar Upper Canada, General Prevost was in the unusual position of having to purchase many provisions for his troops from the American side. This peculiar trade persisted throughout the war in spite of an abortive attempt by the US government to curtail it. In Lower Canada, which was much more populous, support for Britain came from the English elite with strong loyalty to the Empire, and from the French elite, who feared American conquest would destroy the old order by introducing Protestantism, Anglicization, republican democracy, and commercial capitalism; and weakening the Catholic Church. The French inhabitants feared the loss of a shrinking area of good lands to potential American immigrants.[76]
In 1812–13, British military experience prevailed over inexperienced American commanders. Geography dictated that operations would take place in the west: principally around Lake Erie, near the Niagara River between Lake Erie and Lake Ontario, and near the Saint Lawrence River area and Lake Champlain. This was the focus of the three-pronged attacks by the Americans in 1812. Although cutting the St. Lawrence River through the capture of Montreal and Quebec would have made Britain's hold in North America unsustainable, the United States began operations first in the western frontier because of the general popularity there of a war with the British, who had sold arms to the Native Americans' opposing the settlers.
The British scored an important early success when their detachment at St. Joseph Island, on Lake Huron, learned of the declaration of war before the nearby American garrison at the important trading post at Mackinac Island in Michigan. A scratch force landed on the island on July 17, 1812 and mounted a gun overlooking Fort Mackinac. After the British fired one shot from their gun, the Americans, taken by surprise, surrendered. This early victory encouraged the natives, and large numbers moved to help the British at Amherstburg.
An American army under the command of William Hull invaded Canada on July 12, with his forces chiefly composed of untrained and ill-disciplined militiamen.[77] Once on Canadian soil, Hull issued a proclamation ordering all British subjects to surrender, or "the horrors, and calamities of war will stalk before you." He also threatened to kill any British prisoner caught fighting alongside a native. The proclamation helped stiffen resistance to the American attacks. Hull's army was too weak in artillery and badly supplied to achieve its objectives, and had to fight just to maintain its own lines of communication.
The senior British officer in Upper Canada, Major General Isaac Brock, felt that he should take bold measures to calm the settler population in Canada, and to convince the aboriginals who were needed to defend the region that Britain was strong.[77] He moved rapidly to Amherstburg near the western end of Lake Erie with reinforcements and immediately decided to attack Detroit. Hull, fearing that the British possessed superior numbers and that the Indians attached to Brock's force would commit massacres if fighting began, surrendered Detroit without a fight on August 16. Knowing of British-instigated indigenous attacks on other locations, Hull ordered the evacuation of the inhabitants of Fort Dearborn (Chicago) to Fort Wayne. After initially being granted safe passage, the inhabitants (soldiers and civilians) were attacked by Potowatomis on August 15 after traveling only 2 miles (3.2 km) in what is known as the Battle of Fort Dearborn.[78] The fort was subsequently burned.
Brock promptly transferred himself to the eastern end of Lake Erie, where American General Stephen Van Rensselaer was attempting a second invasion. An armistice (arranged by Prevost in the hope the British renunciation of the Orders in Council to which the United States objected might lead to peace) prevented Brock from invading American territory. When the armistice ended, the Americans attempted an attack across the Niagara River on October 13, but suffered a crushing defeat at Queenston Heights. Brock was killed during the battle. While the professionalism of the American forces would improve by the war's end, British leadership suffered after Brock's death. A final attempt in 1812 by American General Henry Dearborn to advance north from Lake Champlain failed when his militia refused to advance beyond American territory.
In contrast to the American militia, the Canadian militia performed well. French Canadians, who found the anti-Catholic stance of most of the United States troublesome, and United Empire Loyalists, who had fought for the Crown during the American Revolutionary War, strongly opposed the American invasion. However, many in Upper Canada were recent settlers from the United States who had no obvious loyalties to the Crown. Nevertheless, while there were some who sympathised with the invaders, the American forces found strong opposition from men loyal to the Empire.