In July of 1781, an American privateer sailing out of New London, Connecticut captured the British merchantman the Hanna, loaded with a bounty of luxury goods destined for British officers based in New York City. That action induced the British supreme leader of British forces in America to grant permission to the infamous traitor Benedict Arnold to lead an 1,800-man punitive amphibious expedition to destroy the American privateer base in New London. Being a native of the region, Arnold-a former American general-had intimate knowledge of the port and its defenses, including the most powerful fortification defending the harbor from Groton Heights Fort Griswold. So important was the fort that Arnold dedicated half of his expeditionary force to landing on the east side of the Thames River, for the sole purpose of capturing the fort and putting its heavy cannon out of commission.
But Arnold miscalculated and misapprehended the strength of the fort and its defenders. That misperception would have grievous consequences for the fort’s British attackers and their outnumbered American defenders.