On September 6, 1781, the Battle of Groton Heights was fought between a combined force of state troops and local militia led by William Ledyard and numerous British forces led by Benedict Arnold. No one at Fort Griswold had expected an attack, especially after six years of false alarms. At sunrise, a force of 1,700 British regulars landed on both sides of the mouth of the Thames River. The fleet had sailed from Long Island the evening before, and only a sudden shift in the wind prevented a surprise attack during the night; it was 9 a.m. the next day before the transports could come ashore to land the troops.