A graduate of Yale University, Hale joined a Connecticut regiment in 1775 and served in the successful siege of British-occupied Boston. On September 10, 1776, he volunteered to cross behind British lines on Long Island to spy on the British in preparation for the Battle of Harlem Heights.
Disguised as a Dutch schoolmaster, the Yale-educated Hale slipped behind British lines on Long Island and successfully gathered information about British troop movements for the next several weeks. While Hale was behind enemy lines, the British invaded the island of Manhattan; they took control of the city on September 15, 1776. When the city was set on fire on September 20, British soldiers were told to look out for sympathizers to the Patriot cause. The following evening, September 21, Hale was captured while sailing Long Island Sound, trying to cross back into American-controlled territory. Although rumors surfaced that Hale was betrayed by his first cousin and British Loyalist Samuel Hale, the exact circumstances of Hale's capture have never been discovered.
Hale was interrogated by British General William Howe and, when it was discovered that he was carrying incriminating documents, General Howe ordered his execution for spying, which was set for the following morning. After being led to the gallows, legend holds that the 21-year-old Hale said, "I only regret that I have but one life to give for my country." There is no historical record to prove that Hale actually made this statement, but, if he did, he may have been inspired by these lines in English author Joseph Addison's 1713 play Cato: "What a pity it is/That we can die but once to serve our country."