It’s not always easy to tell who your true enemies are. Sometimes they claim to be the ones most loyal to your cause. Maybe they even hold positions of power and trust in the government. Such was the case of Doctor Benjamin Church, named the first surgeon-general of the United States Army by George Washington.

The 35-year-old Harvard-graduate and London-trained Renaissance man was one of the most accomplished surgeons in Boston. In 1770, he performed the autopsy on the first man killed in the Boston Massacre—offering his scientific expertise to declare the British soldiers involved in the incident to be murderers.  

A Son of Liberty and close friend of Patriots like Samuel Adams and Doctor Joseph Warren, the doctor made great pains to disguise his true loyalties to the British Crown. He even sprinkled blood on his stockings and showed them to Paul Revere to create the illusion he had been in the thick of the battle. As skillful with words as with a scalpel, Church published poetry and delivered rousing oratory in support of the Patriot cause, both often tinted with his trademark biting sarcasm.

A radical Whig, Freemason, as well as a member of the Sons of Liberty, he traveled in all the right circles of Whig politics and emerged as one of the leading men in Boston. But the surgeon also appreciated the finer things in life and built an elaborate summer home, along with a mountain of debt, which forced him to seek additional sources of revenue. Known for his infidelities to his English wife, he frequently sought the company of the fairer sex, later including a mistress in the town of Marblehead, Massachusetts, which would prove to be his undoing. 

The full story of Doctor Church’s betrayal is now told in the new bestselling book, The Indispensables: Marblehead’s Diverse Soldier-Mariners Who Shaped the Country, Formed the Navy, and Rowed Washington Across the Delaware. The book is a Band of Brothers-style treatment of the regiment from Marblehead, Massachusetts, a unique largely unknown group of Americans who changed the course of history. 

Seemingly a firebrand Son of Liberty, based on his speeches and what flowed from his pen, Church cloaked a darker side and worked for another cause. As early as January 1772, Massachusetts Governor Thomas Hutchinson indicated that the Crown paid Church handsomely to write anonymous articles. His patriotic ardor and arrogance disguised a heavily indebted opportunist who craved wealth. By 1775, 40-year-old Church sat alongside Marblehead’s leading families on the government committees that guided some of the most important decisions of the early Patriot movement. The haughty, sarcastic Church participated in all the crucial meetings—and promptly passed the information on. He was General Gage’s most well-placed spy—directly in the middle of the Patriot nerve center. 

Church not only passed along priceless information, like the locations of the Patriots’ hidden caches of arms and munitions throughout eastern Massachusetts, including the arms at Salem or at Concord which prompted the first famed shots of the Revolution, but also his surprisingly cogent and prescient analysis of their weaknesses and strengths, such as “their adroitness in the habitual use of the firelock [who] suppose themselves sure of their mark at 200 yards.”

As the Congress deliberated and shaped the new government, Church enthusiastically participated on committees where he carefully spun a web of lies and captured some of the Revolution’s most important intelligence. From his perch in the Provincial Congress, Gage’s top spy had an unparalleled vantage point to view the inner workings of the fledgling government. Days after Lexington and Concord, the good doctor stunned the Committee of Safety by boldly proclaiming he was traveling to Boston the next day. The room was aghast. “Are you serious, Doctor Church?” Warren incredulously retorted. “They will hang you if they catch you in Boston.” The siege on Boston had rattled Church’s plan to deliver his intelligence to Gage, so he needed a plausible excuse and means to break through the lines and get into the city. He dug in his heels: “I am serious, and I am determined to go at all adventures.” 

After considerable debate, Congress agreed to make a plausible excuse for the doctor—getting medicine for wounded British and American troops. Church passed through the lines the next day. For appearance’s sake, he was taken prisoner. But once within the arms of the British, he rode in style, as Gage furnished him with a carriage to British headquarters, where he disgorged his priceless intelligence on the inner workings and plans of the Committee of Safety. Remarkably, after the meeting, he walked freely around occupied Boston and returned through American lines with the medicine and, unknown to his fellow Patriots, a sack full of British money for his betrayal as he resumed his powerful position on the Provincial Congress.

The Patriots finally uncovered Church’s treachery when he attempted to use his Marblehead mistress, Mary Wenwood, as a courier after several other avenues of communication failed him.  Wenwood aroused the suspicion of her former husband. She asked for his help in procuring a meeting with the Newport customs officer or the captain of a British warship patrolling Newport Harbor to forward a communication from Cambridge on to besieged Boston. Her former husband, Godfrey Wenwood, convinced her to give him the letter, which he held for some time before opening it and alerting the Patriots. The indecipherable language of the letter raised even more alarms. 

General Washington called for the woman to be arrested and interrogated. Doctor Benjamin Church finally emerged as the author of the letter. Immediately taken into custody, the surgeon general vehemently denied the accusation of treacherous behavior but failed to produce the key to the coded letter in question. Marbleheader Elbridge Gerry scrambled to break the code. He enlisted the services of expert decipherer Elisha Porter. Together the two men discovered that Church had used a substitution cipher, replacing each letter of the alphabet with a symbol. The contents of the letter revealed the amount of gunpowder the Patriots possessed, the condition of their army, and their expected movements. Church continued to plead his innocence, but a court-martial convicted the Son of Liberty. 

Evidence at the time proved inconclusive to execute Church, and only decades later would his intelligence reports to Gage surface proving he was a spy, so Massachusetts exiled him instead. His ship left Boston Harbor in January 1778 for the Caribbean: the vessel and Doctor Benjamin Church were never seen again.

Patrick K. O’Donnell is a bestselling, critically acclaimed military historian and an expert on elite units. He is the author of twelve books, including The Indispensables, which is featured nationally at Barnes & Noble, Washington’s Immortals, and The Unknowns. O’Donnell served as a combat historian in a Marine rifle platoon during the Battle of Fallujah and often speaks on espionage, special operations, and counterinsurgency. He has provided historical consulting for DreamWorks’ award-winning miniseries Band of Brothers and documentaries produced by the BBC, the History Channel, and Discovery. PatrickODonnell.com @combathistorian