Key figures: David Bushnell, Ezra Lee, Admiral Richard Howe, George Washington, Isaac Doolittle
Summary
On the night of September 6–7, 1776, Sergeant Ezra Lee piloted a hand-powered submersible vessel called the Turtle through New York Harbor in an attempt to attach an explosive charge to the hull of HMS Eagle, the flagship of British Admiral Richard Howe. The mission failed — the boring device could not penetrate the ship’s copper-sheathed hull fittings — but the episode stands as the first recorded use of a submarine in warfare. The Turtle was the invention of David Bushnell of Connecticut, who had conceived, designed, and built it between 1771 and 1775 while studying natural philosophy at Yale College.
Bushnell’s vessel embodied four capabilities that later engineers would identify as the essential requirements for a military submarine: the ability to submerge and resurface; the ability to maneuver underwater; an adequate air supply for the operator; and the capacity to deliver an offensive weapon against an enemy surface ship. Although the Turtle never sank a British vessel, it established the concept of submarine warfare, and Bushnell is widely remembered as the “father of submarine warfare.”
Design and Construction
Bushnell was born around 1740 in what is now Westbrook, Connecticut, and entered Yale College at the unusually advanced age of thirty-one in 1771, after selling his share of the family farm. At Yale he studied mathematics, geometry, and natural philosophy, gaining access to contemporary scientific texts through the college library. He began designing the Turtle during his studies and continued refining it after graduation. The Connecticut clockmaker Isaac Doolittle crafted the vessel’s precise brass and mechanical components; Phineas Pratt also assisted with the construction.
The hull was built from oak planks sealed with tar and reinforced with iron hoops, shaped to resemble two turtle shells joined together — the origin of the craft’s name. The vessel measured approximately ten feet long, six feet tall, and three feet wide, and was operated by a single occupant who sat upright inside. A hatch fitted with six small glass ports admitted limited light; for use underwater at night, the instrument needles were marked with foxfire, a bioluminescent fungus that glowed faintly in the dark.
Propulsion relied on a hand-cranked screw propeller for horizontal movement and a second foot-operated propeller for vertical movement — the first known application of a screw propeller to any watercraft. Depth was controlled by flooding a foot-operated ballast tank with water to submerge and pumping it out by hand to ascend; an additional 200 pounds of lead ballast provided stability and could be released in an emergency. The vessel carried roughly thirty minutes of air for its operator.
The weapon was a keg-shaped mine, approximately two and a half feet long and packed with some 150 pounds of gunpowder. Bushnell designed it to be screwed into the wooden hull of a target ship from below, then triggered by a clockwork-activated flintlock mechanism after the Turtle had withdrawn to a safe distance.
The September 1776 Mission
By mid-1776 the British had deployed a large fleet in New York Harbor under Admiral Richard Howe as part of the campaign to seize New York City from the Continental Army. The Turtle reached New York in August 1776. Bushnell’s brother, who had trained for months to pilot the craft, fell ill before the operation could begin. Sergeant Ezra Lee, an Army volunteer from Lyme, Connecticut, received only basic familiarization training before being selected to carry out the mission.
Lee set out in the Turtle at midnight on September 6, 1776, with HMS Eagle as his target. He maneuvered underwater for approximately two and a half hours against tidal currents in the harbor. Upon reaching the hull of HMS Eagle, Lee repeatedly worked the boring screw in an attempt to drive it into the ship’s wooden bottom so the mine could be attached. The screw failed to penetrate — most accounts attribute the failure to Lee striking an iron fixture near the ship’s rudder hinge, though the exact obstacle is not definitively documented. With his air supply nearly exhausted, daylight approaching, and British guard boats closing in, Lee released the mine and began his withdrawal. The drifting charge detonated in the East River “with tremendous violence,” as contemporary accounts described, but caused no damage to HMS Eagle or any British vessel, and Lee escaped.
Further attempts using the Turtle against British ships in the Hudson River in October 1776 also came to nothing. On October 9, 1776, British frigates sank the sloop that served as the Turtle’s tender; Bushnell stated that he salvaged the submarine, but its final fate and location remain unknown.
Washington’s Assessment and Contemporary Reception
General George Washington, informed of the attempt, offered a measured appraisal: the enterprise showed “an effort of genius,” but “a combination of too many things was requisite” for success. His comments recognized Bushnell’s inventive accomplishment while acknowledging the practical obstacles — inadequate pilot training, strong harbor currents, and the mechanical difficulty of attaching a mine to a moving ship’s bottom at night — that doomed the mission.
Bushnell’s design remained largely secret during the war. After the Revolution, he described his submarine and mine technology in a detailed letter in 1787. Thomas Jefferson transmitted this letter to the American Philosophical Society in 1798, bringing Bushnell’s work to wider learned attention. Bushnell spent the later decades of his life in Georgia under the assumed name David Bush, working as a schoolteacher and physician until his death in 1824.
Significance
- First submarine in combat: The Turtle’s September 7, 1776 mission against HMS Eagle is the first documented use of a submarine in warfare, establishing a new category of military technology.
- First screw propeller: Bushnell’s hand-cranked propellers were the earliest known application of the screw propeller to any watercraft, anticipating the drive systems of modern submarines and ships by decades.
- First water-ballast diving system: The Turtle pioneered flooding and pumping ballast tanks to control depth — the principle that governs submarine buoyancy to the present day.
- First military submarine mine: Bushnell’s clockwork-triggered explosive charge was the earliest practical design for an underwater mine, a weapon type that would play a significant role in later naval warfare.
- Legacy of influence: Although the Turtle never achieved its tactical objective, it demonstrated the theoretical viability of submarine warfare. American naval engineers Robert Fulton and later designers explicitly built on Bushnell’s conceptual framework in developing nineteenth-century submarines.