On his return to New York in June, Arnold made a variety of proposals for attacks on economic targets to force the Americans to end the war. Clinton was uninterested in most of his aggressive ideas, but finally authorized him to raid the port of New London, Connecticut. He led a force of more than 1,700 men which burned most of New London to the ground on 4 September, causing damage estimated at $500,000. They also attacked and captured Fort Griswold across the river in Groton, Connecticut, slaughtering the Americans after they surrendered following the Battle of Groton Heights—and all these deeds were done just a few miles down the Thames River from Norwich, where Arnold grew up. However, British casualties were high; nearly one quarter of the force was killed or wounded, and Clinton declared that he could ill afford any more such victories.