July 21: Testing the World’s First Military Submarine — in 1776


While Connecticut has been home to an outsized share of American innovators and creative geniuses, few of them have had as long-lasting an impact as David Bushnell, inventor of the Turtle — the world’s first combat submarine.

Born in Saybrook in 1740, Bushnell decided at age 30 to sell his share of the family farm and attend Yale College, where (as a notably older-than-average student in the Class of 1775) his favorite subjects included physics and chemistry.  While at Yale, he engaged in a number of scientific experiments, the most notable resulting in the successful underwater detonation of gunpowder.

After the first shots of the Revolutionary War were fired at Lexington and Concord in April 1775, Bushnell, an ardent patriot, began contemplating how he could weaponize his discoveries to help defeat the British army.  By early 1776, with his brother Ezra’s help, David Bushnell had constructed a working model of a submersible boat designed to anchor underwater timed mines to the hull of enemy ships.  Named the Turtle, the vessel almost defied comprehension by 18th century standards: shaped roughly like a clamshell, the small wooden submarine featured a complex ballast mechanism, used bioluminescent fungi for a light source, and relied on a screw propeller (still used by submarines today) for its propulsion system.

A 19th century illustration of David Bushnell’s Turtle submarine from the Library of Congress.

On July 21, 1776, the Bushnells conducted their first field tests of the Turtle, testing the vessel’s seaworthiness off the coast of Charles Island in Milford, Connecticut.  Evidently pleased with the results, the Turtle embarked on its first combat mission for the Continental Army in September 1776, with Connectican Ezra Lee at the helm.  In what was perhaps one of the most audacious missions of the entire Revolutionary War, Lee piloted the awkward submarine into New York Harbor in an attempt to attach an underwater mine to the hull of the HMS Eagle — the flagship of British Admiral Richard Howe.  Although Lee did manage to reach the Eagle’s hull, a number of factors including rough tides prevented him from successfully attaching his mine to the ship, rendering the Turtle’s only mission a failure.

After concluding that the Turtle was too unwieldy to be a reliable weapon against the British, David Bushnell focused on developing floating mines and later served as a captain in the American Corps of Sappers and Miners.  His most notable contribution to American history, however, remains his incredible Turtle submarine — an invention that ultimately changed the course of military history around the world.

Further Reading

Brenda Milkovsky, “David Bushnell and his Revolutionary Submarine,” connecticuthistory.org

The Submarine Turtle,” Naval History and Heritage Command website