The first of the defeats was Fort Mackinac. A short understanding of what took place there--

"""At the start of the War of 1812, the fort was manned by a small U.S. garrison of approximately 60 men under the command of Lt. . British General Isaac Brock, having anticipated the start of war, sent a canoe party 1200 miles (1900 km) to confirm that a state of war existed. The American commander Hanks, however, received no notification of the start of the conflict. On the morning of July 17, 1812, a British and Native American combined force of seventy war canoes and ten landed on the north end of the island, 2 mi (3.2 km) away from the fort. The British quietly removed the village inhabitants from their home and trained two cannon at the fort. The American commander, taken completely by surprise, realized he was badly outnumbered, and fearing a massacre by the Native Americans on the British side, accepted the British offer of surrender without a fight. The American force was taken prisoner and the island inhabitants were made to swear an oath of allegiance as subjects of the United Kingdom. After capturing the island, the British, under the command of Colonel of the Royal Newfoundland Regiment, also built a stockade and blockhouse on the island's highest point, renaming it as Fort George. ""

The prior from Wikipedia.