Hale accepted a commission as first lieutenant in the 7th Connecticut Regiment under Colonel Charles Webb of Stamford. Hale was also a part of Knowlton's Rangers, the first organized intelligence service organization of the United States of America, led by Lieutenant Colonel Thomas Knowlton. In the spring of 1776, the Continental Army moved to Manhattan to defend New York City against the anticipated British attack. In August, the British soundly defeated the Continentals in the Battle of Long Island via a flanking move from Staten Island across Brooklyn.

An account of Hale's capture, later obtained by the Library of Congress, was written by Consider Tiffany, a Connecticut shopkeeper and Loyalist. In Tiffany's account, Major Robert Rogers of the Queen's Rangers saw Hale in a tavern and recognized him. After luring Hale into betraying his allegiance by pretending to be a Patriot himself, Rogers and his Rangers apprehended Hale near Flushing Bay in Queens, New York.

On the morning of September 22, 1776, Hale was marched along Post Road to the Park of Artillery, which was next to a public house called the Dove Tavern (at modern-day 66th Street and Third Avenue), and hanged. He was 21 years old.