Meantime a very important victory had been scored by the British at Mackinaw Island, at the northwest extremity of Lake Huron, where there was a fortified United States post. Fort St. Joseph, a British post established for the protection of the fur trade, was situated on an island at the debouchure of Lake Superior into the waters of Lake Huron, Captain Roberts, a brave and energetic officer, being in command. Brock had rein-forced this post in the spring, and Roberts had received instructions to try to capture Mackinaw. With a force of 45 regulars, 400 Indians, 180 French-Canadian voyageurs—half of them armed with fowling-pieces and old muskets, and two iron 6-pounders, Roberts embarked in a flotilla of boats and canoes, attended by a small brig laden with stores. On July 17th he landed on Mackinaw Island unmolested, got one of his guns into a menacing position for storming operations, and bade the Indians and half-breeds yell the war-whoop. The United States commander, who knew nothing of the outbreak of war and was quite unprepared for an attack, surrendered his post, with sixty-one men and a large quantity of stores and valuable furs. This well-executed stroke secured the adhesion of the Indians; disconcerted Hull, by exposing his rear; and Mackinaw was retained by the British until the end of the war.
Brock, taking advantage of the British control of Lakes Ontario and Erie, assumed the offensive against Hull at Detroit. Leaving York (Toronto), the capital of Upper Canada, on August 6th, he went by boat to Burlington Bay, thence overland to Long Point on Lake Erie; here he picked up forty of the 41st Regiment and 260 militia-men and went on by water to Amherstburg, which he reached on August 13th. Proceeding to Sandwich, opposite Detroit, on the 15th, he summoned Hull to surrender. Hull took two hours to consider the summons and declined it; Brock thereupon determined to cross the river and attack Fort Detroit. That night Tecumseh was sent in advance to the American shore with about 600