Despite its isolated location, Fort Michilimackinac on Mackinac Island at the western end of Lake Huron was an important American possession at the start of the War of 1812. The British believed that they would need Indian support to defend Upper Canada against an American attack. If the Americans retained control of Mackinac Island then they would be in a good position to deny the British that support. The importance of the island had been recognised in the aftermath of the Treaty of Paris of 1783. In that treaty it had been placed on the American side of the border, but it had then been retained by the British until 1796 in order to maintain contact with their Indian allies. When it was finally transferred to the United States the British garrison moved fifty miles east to Fort St. Joseph, an island in the St. Mary’s River.
Even though it was the Americans who declared war in 1812, Lieutenant Porter Hanks, the commander at Fort Michilimackinac would only learn of the outbreak of war when he was attacked. His position was not strong. The fort had been built on a limestone bluff overlooking the harbour at the south east end of the island. It was armed with 9-pdr guns, but they were unable to control the waterway linking Lake Michigan to Lake Huron, or even protect the fort’s water supply. Hanks had a garrison of 61 United States regulars to defend his position.
Captain Charles Roberts, the British commander at Fort St. Joseph was in no better a position. His own fort was even weaker that Fort Michilimackinac, while he described his 45 regulars from the 10th Royal Veterans as obedient but “worn down by unconquerable drunkenness”, a common complaint about British regulars in Canada at the start of the war. News of the American declaration of war reached Roberts on 8 July, along with an order to attack Fort Michilimackinac. This clear message was followed by a series of alternating orders encouraging and then cancelling the attack, before finally he received an order to use his own initiative.
Roberts’s chances of success were greatly increased by the help he received from the North West Company and from a variety of Indian tribes. The company provided 180 Canadian and half-breed employees, and the schooner Caledonia. Two parties of Native Americans provided him with 300 Ojibways and Ottawas and 110 Sioux, Menominee and Winnebago Indians. On 16 July Roberts embarked this force on the Caledonia and a flotilla of canoes, reaching Mackinac Island at 3am on 17 July. During the 50 mile journey he had captured an American scout. Upon landing on the island, Roberts released his prisoner and told him to warn the local villages to move to the opposite end of the island. Instead, the local doctor warned Hanks in the fort.
By now it was too late. The Canadians had managed to get a 6-pdr onto the top of a hill that overlooked the fort. Hanks was outnumbered by almost ten-to-one and his fort was not built to withstand even a small scale artillery bombardment. At 10am Captain Roberts summoned Hanks to surrender. Aware of his hopeless position, and concerned that his troops might be massacred by the Indians if a fight developed, Hanks agreed to surrender with the full honours of war. Three British deserters in the garrison were seized, but otherwise his men were freed on parole. Much to Robert’s pleasure his Indian allies then returned to their canoes without any problems. Later British victories would be marred in many eyes by massacres after the battle. In the aftermath of his victory, Roberts moved his base to Fort Michilimackinac.
The capture of Mackinac Island transformed the situation in Upper Canada. The British retained control of the area throughout 1813, and were able to make great use of their Indian allies in the fighting to the east. The news of the American defeat at Mackinac Island also played a significant part in the British capture of Detroit. At the start of the war an American expedition under Brigadier-General Hull had crossed over the Detroit River into Canada, but had failed to make any further progress. Hull was already beginning to lose his nerve before news of the British victory on Lake Huron was confirmed on 2 August. After considering launching an attack on the British position at Fort Malden, on 8 August he retreated back to Detroit. On 16 August, under pressure from a British attack, he surrendered Detroit and his entire force.