ON JULY 2, 1812, the schooner Cuyahoga, a private American vessel, sailed from Lake Erie into the mouth of the Detroit River and past Fort Amherstburg, a British stronghold on the Canadian side of the river. Unknown to those on board, the United States had formally declared war against Great Britain. But the British at Amherstburg knew. They seized the ship from the surprised crew and were rewarded with papers belonging to American brigadier general William Hull. Among them: correspondence outlining an invasion of Canada.

It was quite a coup. Days into the War of 1812, British held the plans for a key American strike, complete with troop strength and insights into the enemy commander's state of mind. Armed with these secrets, the redcoats over the next few weeks would turn the tables on the Americans, launch their own invasion, and force the only surrender of a U.S. city to a foreign army.

When American leaders declared war on Britain on June 18, 1812, they described it as a second fight for liberty. The country was outraged by the impressment of U.S. sailors into Royal Navy service, not to mention British collusion with Indians to block American expansion in frontier territories such as Michigan and Indiana. But Americans also coveted the rich farmland of British-held territories to the north. "The conquest of Canada is in your power," Speaker of the House Henry Clay of Kentucky had crowed to his colleagues in February 1810, boasting that his state's militia alone was enough "to place Montreal and Upper Canada at your feet."