Home Connecticut Benedict Arnold’s Treason Unmasked to Washington—in Arnold’s Own House

Benedict Arnold’s Treason Unmasked to Washington—in Arnold’s Own House

The traitor made a quick getaway

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George Washington learned about Benedict Arnold’s treason while staying at Benedict Arnold’s house near West Point. He wondered why Arnold, his best battlefield commander, wasn’t there. As he was getting ready for dinner, Alexander Hamilton brought him the news.

Arnold had vanished moments before Washington rode up to the sprawling mansion along the Hudson River. He had received a letter telling him that Washington knew, or would soon know, that the jig was up. The Americans had arrested a suspicious person with incriminating evidence in Arnold’s handwriting, the letter said.

Benedict Arnold

Arnold had received the dispatch over breakfast with two of Washington’s aides. They had gone to Arnold’s house ahead of the rest of the commander-in-chief’s entourage. Arnold had excused himself and gone somewhere on urgent business–to the fort, he told them.

They never saw him again.

Benedict Arnold’s Treason

Benedict Arnold’s treason stemmed from a web of motives. They included a desire to avenge his honor, a measure of greed, painful and crippling battle wounds and the influence of his Loyalist wife.

By the time Washington showed up at his house, he had already given the British information about planned American troop movements.

He was born Jan. 14, 1741 in Norwich, Conn., into a once-prominent New England family. His great-grandfather, also Benedict Arnold, had served as governor of Rhode Island. His great-great-grandfather, William Arnold, had established King’s Chapel in Boston. Benedict Arnold spent his boyhood in affluence, but his alcoholic father then squandered all his money.

His father’s failure meant Arnold couldn’t attend Yale, and it also gave him a thirst for money and honor. He succeeded at merchant shipping and privateering, only to lose practically everything in the patriot cause. When he turned traitor he demanded £20,000 for his services.

Col. Benedict Arnold, before his promotion to general

He had served the cause valiantly, capturing Fort Ticonderoga, leading the expedition to Quebec, stopping a British invasion at the Battle of Valcour Island. Arnold had also helped drive the British from Connecticut and led American forces to victory at Saratoga.

His men loved him. Congress did not, passing him over for promotion in favor of junior—and less heroic — men. His nemesis, Gen. Horatio Gates, hadn’t even mentioned Arnold’s name in his report about the Battle of Saratoga.

Love of Money

Arnold’s love of money got him into trouble. While he recovered from severe wounds at Saratoga (add photo of boot), Washington appointed him military governor of Philadelphia. The British had recently evacuated, and he fell in love with 18-year-old Peggy Shippen, from a prominent Loyalist family. They married April 8, 1779.

Peggy Shippen Arnold

Peggy liked to live large, as did her husband, and they led an ostentatious lifestyle. Arnold engaged in war profiteering, which led to his court martial.  Though acquitted on several counts, the court recommended a reprimand for several minor transgression. Washington sent him a letter chastising him as gently as he could, but Arnold — crippled, bitter and married to a Loyalist — had already put out feelers to the British.


Benedict Arnold’s treason resulted from patriotic motive, or so he told himself—and, later, Washington. The war in 1780 wasn’t going well. Congress dithered and failed to provide for the Continental Army, which suffered from poor morale. Currency inflation started spinning out of control.  The alliance with France hadn’t produced any victories. Then in May came the worst defeat of the war when Gen. Benjamin Lincoln and his 10,000 troops surrendered unconditionally in Charleston, S.C. Washington despaired.


George Washington, 1776

The British had also made overtures for peace, giving the Americans almost everything they wanted except for independence.

Arnold wasn’t the only one who considered changing sides. Charles Lee, captured by the British, shared with them a plan to defeat the Continental Army.

And Ethan Allen negotiated with the British on behalf of Vermont for a separate peace. He wanted to protect his extensive land holdings and the British offered to recognize Vermont as an independent state, part of the British Empire.

Had some things gone differently, perhaps Benedict Arnold’s treason wouldn’t have happened. He wanted a naval command. He had plenty of experience at sea, and he felt his wounds made him unfit for battle on land. But Washington didn’t see it that way.

West Point

He ended up finagling command of West Point, a key American position on the Hudson River. Upon his arrival on August 25, Arnold began to dismantle the fort’s defenses. He didn’t make needed repairs and he sent two cannons away, ostensibly to get refurbished. Then he sent 500 men off to cut wood and another 200 north to guard Fishkill, N.Y.


The Beverly Robinson house.

The Arnolds – Benedict, Peggy and baby Edward – moved into a house two miles down the Hudson from the fort and on the other side. The house had belonged to wealthy Loyalist Col. Beverly Robinson, who helped Arnold change sides.

Arnold had been begging the British for a meeting with their spymaster, Maj. John Andre. The first attempt failed. Then in late September Andre sailed up the Hudson on the sloop of war HMS Vulture. On the evening of September 21, Arnold sent two men in a boat to pick up Andre. They didn’t want to do it, but Arnold threatened to arrest them. They rowed out, picked up Andre and took him to shore, where Arnold waited with another horse. The two men talked at the Joshua Smith house in Haverstraw, N.Y. Meanwhile, Continental troops spied the Vulture and began bombarding the vessel, forcing it to move downriver.


John Andre

The Vulture’s departure stranded Andre. So Arnold gave him civilian clothes, a letter of transit under the assumed name John Anderson and intelligence about West Point. Andre’s superior officer, Gen.  Sir Henry Clinton, had expressly told him not to do those three things.

Caught Out

Arnold returned to his headquarters on the banks of the Hudson. Two days later, he sat down to breakfast with Capt. Samuel Shaw and Maj. James McHenry.

They had been traveling with Washington and arrived in advance of the general’s expected visit that day. Washington had told them to go on ahead while he inspected redoubts along the way. But his entourage — including Henry Knox, Alexander Hamilton and the Marquis de Lafayette – stayed with Washington.

Arnold invited Shaw and McHenry to have breakfast with him while Peggy stayed upstairs with the baby. Then Lt. Solomon Allen arrived with a message for Arnold from Continental Army Col. John Jameson.

West Point from Phillipstown, 1831

Jameson wrote he found incriminating papers in the stocking of a suspicious person claiming to be John Anderson. He had sent the papers to Washington. Arnold realized they had captured Andre – “John Anderson” – and he would soon be unmasked.

As Arnold read the message he showed a moment of distress but quickly regained his composure. He excused himself and went outside to tell his servant to get a horse and alert his bargemen. Then he went upstairs to tell his wife he had to leave immediately to join the British. She fainted on the bed. Just then one of Washington’s light horsemen knocked on the bedroom door and told him Washington would arrive momentarily.

Col. John Jameson

Arnold then told his breakfast companions he had to go across the river to the fort to prepare for Washington’s visit. His horse didn’t await him, so he took the messenger’s horse. He galloped down to the river, where oarsmen waited to take him up the river to the fort. Or so they presumed.

Arnold ordered them downriver instead, offering them two gallons of rum each if they would row with all their might. When they approached the Vulture, he held up a white handkerchief. Arnold and the oarsmen boarded the vessel, and Arnold told them they were now prisoners. The men protested, but they were paroled when they arrived in New York.

Washington Finds Out

Moments after Arnold left, Washington rode up to the house. Told Arnold had gone to the fort, he ate a quick breakfast and went to the fort with Knox and Lafayette. Hamilton stayed behind in case any dispatches arrived. They agreed to meet back at the house for dinner, scheduled for 4 p.m.

Alexander Hamilton and Henry Knox

Washington expected a military salute when he approached the fort, but none came. Mystified, he was approached by the fort’s commandant, Col. John Lamb, who apologized for the inadequate reception. He hadn’t known Washington was coming.

Washington then asked to see Arnold. Lamb said he hadn’t showed up in two days. Washington then proceeded to inspect the fort, all the while asking about Arnold’s whereabouts.

When Washington, Knox and Lafayette returned to the Robinson house, they expected Mr. and Mrs. Arnold to greet them. But he had disappeared and she was still upstairs, indisposed. Washington went to his room to prepare for dinner when Hamilton handed him a sheaf of dispatches.

Washington then read the news of Arnold’s betrayal. He asked Hamilton and Lafayette to join him. “Arnold has betrayed us,” he said. “Whom can we trust now??


Washington ordered Hamilton to gather some men to intercept Arnold downriver. Then Arnold’s aide, Lt. Col. Richard Varick, came to Washington’s room and told him Mrs. Arnold seemed to have gone mad.

Washington then went to see Peggy, who he had known since girlhood. Peggy Shippen Arnold put on quite a show for him, thrashing, crying and raving deliriously. She convinced Washington, and for many years historians, that she knew nothing of Benedict Arnold’s treason. Her feigned madness gave her husband more time to escape.

Washington believed Benedict Arnold’s treason had unhinged his wife. He let her alone for dinner, and told no one else of Arnold’s treason. “Mrs. Arnold is sick and General Arnold is away,” Washington said. “We must therefore take our dinner without them.”

They barely touched their meal. Arnold’s aides, Lt. Col. Richard Varick and Maj. David Franks, had figured out Benedict Arnold’s treason. They knew they were under suspicion and covertly watched Washington to suss out what he knew. Washington and his officers did the same to them. “Never was there a more melancholy dinner,” Lafayette said years later. “The General was silent and reserved, and none of us spoke of what we were thinking about.”

After dinner, Washington asked Varick to stop outside. He told him about Benedict Arnold’s treason. Then he said he had no reason to suspect him or Franks, but they must consider themselves under arrest.

Peggy Shippen

Peggy had flirted with Andre during the British occupation of Philadelphia. Within a month of her marriage, Arnold corresponded with Andre. Later, evidence of Peggy’s involvement in Benedict Arnold’s treason came to light. The British had paid her £350 for handling secret letters.

The President’s House, Philadelphia, where Arnold lived as military general

Washington received a letter from Arnold, telling him Peggy didn’t know he’d turned traitor, and asking him to grant her safe passage to her family in Philadelphia. Washington gave her a choice: She could join her husband in New York or her family in Philadelphia. She chose Philadelphia.

At the same time, Washington intended to punish Benedict Arnold. He organized an attempt to track him down in New York, one that nearly succeeded. Had Arnold been captured, he would have been summarily hanged.


Andre went to the gallows on Oct. 2. A court martial exonerated Franks and Varick.

The British gave Arnold the rank of brigadier general, and he led his forces on destructive rampages through Virginia and Connecticut.  Peggy eventually joined him in New York. After Cornwallis’s surrender at Yorktown, the Arnold family left for London.

A few years later, Arnold returned to North America, settling in Canada to speculate in land and start a merchant shipping business. The family then returned to London, where Benedict Arnold died in 1801 at the age of 60. Peggy died three years later at the age of 44.

In 1781, American agents a letter that said the British had paid only £5,000 for Benedict Arnold’s treason, not the £20,000 he had demanded. Franklin wrote to Lafayette, calling it “a miserable bargain especially when one considers the quantity of infamy he has acquired to himself and entailed on his family.”

With thanks to Benedict Arnold: How The Traitor Was Unmasked by James Thomas Flexner, American Heritage, 1967; The Life and Treason of Benedict Arnold by Jared Sparks, 1851. This story updated in 2023.

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