On October 5, 1775, General George Washington writes to the president of the Continental Congress, John Hancock, to inform him that a letter from Dr. Benjamin Church, surgeon general of the Continental Army, to Lieutenant General Sir Thomas Gage, British commander in chief for North America, had been intercepted. Washington wrote, “I have now a painful tho’ a Necessary Duty to perform respecting Doctor Church, Director General of the Hospital.”

Washington described how a coded letter to a British officer, Major Crane, came into Washington’s possession by a convoluted route from “a Woman who was kept by Doctor Church.” Washington “immediately secured the Woman, but for a long time she was proof against every threat and perswasion[sic] to discover the Author, however, at length she was brought to a confession and named Doctor Church. I then immediately secured him and all his papers.”

The woman Washington interrogated was the mistress of Dr. Benjamin Church, a renowned Boston physician, who was active in the Massachusetts Committee of Safety and served as a member of the Provincial Congress. In July 1775, Washington had named Church the first surgeon general of the Continental Army, only to find out three months later that he had been spying for the British since 1772. Church faced an army court martial on October 4, 1775.

Source: history.com