In the first week of September, 1776, the American army defending New York still held Manhattan Island, but nothing more. Hastily improvised, badly equipped, and worse disciplined, it had been easily defeated by a superior invading force of British regulars and German mercenaries in the battle of Long Island. Brooklyn had fallen; from Montauk Point to the East River, all was the enemy's country. Staten Island, too, was an armed and hostile land. After the fall of the forts on both sides of the Narrows, the British fleet had entered the Upper Bay, and even landed marines and infantry on Governor's Island. Grimly guarding the crowded transports, the ship-of-the-line Asia and the frigate Eagle lay a little above Staten Island, with their broadsides trained on the doomed city.
In the mouth of the North River, not a biscuit-toss from the Battery, floated the brass conning-tower of an American submarine.
It was the only submarine in the world and its inventor called it the Turtle. He called it that because it looked like one: a turtle floating with its tail down and a conning-tower for a head. It has also been compared to a modern soldier's canteen with an extra-large mouthpiece, or a hardshell clam wearing a silk hat. It was deeper than it was long and not much longer than it was broad. It had no periscope, torpedo tubes, or cage of white mice. But the Turtle was a submarine, for all that.