Historians have identified many possible factors contributing to Arnold's
treason, while some debate their relative importance. According to
W. D. Wetherell, Arnold was: Wetherell says that the shortest explanation for Arnold's treason is that he "married the wrong person." As early as 1778, there were signs that Arnold was unhappy with his situation and pessimistic about the country's future. On November 10, 1778, Major General
Nathanael Greene wrote to Brigadier General
John Cadwalader, "I am told General Arnold is become very unpopular among you owing to his associating too much with the Tories." A few days later, Arnold wrote to Greene and lamented over the "deplorable" and "horrid" situation of the country at that particular moment, citing the
depreciating currency, disaffection of the army and internal fighting in Congress, while predicting "impending ruin" if things did not change soon. Biographer
Nathaniel Philbrick argues:
Secret communications lines by Arnold are interspersed with lines by his wife, Peggy. Early in May 1779, Arnold met with Philadelphia merchant Joseph Stansbury, who then "went secretly to New York with a tender of [Arnold's] services to Sir Henry Clinton." Stansbury ignored instructions from Arnold to involve no one else in the plot, and he crossed the British lines and visited
Jonathan Odell in New York. Odell was a Loyalist working with
William Franklin, the last colonial governor of
New Jersey and the son of
Benjamin Franklin. On May 10, Franklin introduced Stansbury to André, who had just been named the British spy chief. This was the beginning of a secret correspondence between Arnold and André, sometimes using Shippen as a willing intermediary, which culminated more than a year later with Arnold's change of sides. This initial letter opened a discussion on the types of assistance and intelligence that Arnold might provide and included instructions for how to communicate in the future. Letters were to be passed through the women's circle that Arnold's wife was a part of, but only she would be aware that some letters contained instructions that were to be passed on to André, written in
invisible ink, using Stansbury as the courier. The text was encoded using a scheme now known as the
Arnold Cipher, which used
Commentaries on the Laws of England by
William Blackstone as a
cryptographic key. By July 1779, Arnold was providing the British with troop locations and strengths, as well as the locations of supply depots, all the while negotiating over compensation. At first, he asked for
indemnification of his losses and £10,000 (), an amount that Congress had given
Charles Lee for his services in the Continental Army. Clinton was pursuing a campaign to gain control of the
Hudson River Valley, and was interested in plans and information on the defenses of
West Point and other installations on the Hudson River. He also began to insist on a face-to-face meeting and suggested to Arnold that he pursue another high-level command. By October 1779, the negotiations had ground to a halt. Furthermore, revolutionary mobs were scouring Philadelphia for Loyalists, and Arnold and the Shippen family were being threatened. Arnold was rebuffed by Congress and by local authorities in requests for security details for himself and his in-laws.
Court martial , in Morristown, New Jersey, where the trial took place Arnold's court-martial on charges of profiteering began meeting on June 1, 1779, but it was delayed until December by Clinton's capture of
Stony Point, New York, throwing the army into a flurry of activity to react. Several members on the panel of judges were ill-disposed toward Arnold over actions and disputes earlier in the war, yet Arnold was cleared of all but two minor charges on January 26, 1780. Arnold worked over the next few months to publicize this fact; however, Washington published a formal rebuke of his behavior in early April, just one week after he had congratulated Arnold on the birth of his son, Edward Shippen Arnold, on March 19: was Lieutenant General Henry Clinton's spy chief; he was captured and hanged for his role in the plot.|alt=A half-length portrait of André, showing him wearing his army uniform without a hat. Shortly after Washington's rebuke, a Congressional inquiry concluded that Arnold had failed to account fully for his expenditures incurred during the Quebec invasion, and that he owed the Congress some £1,000 () largely because he was unable to document them. Many of these documents had been lost during the retreat from Quebec. Angry and frustrated, Arnold resigned his military command of Philadelphia in late April.
Offer to surrender West Point Early in April 1780, Schuyler had approached Arnold with the possibility of giving him the command at West Point. Discussions had not borne fruit between Schuyler and Washington by early June. Arnold reopened the secret channels with the British, informing them of Schuyler's proposals and including Schuyler's assessment of conditions at West Point. He also provided information on a proposed French-American invasion of Quebec that was to go up the
Connecticut River (Arnold did not know that this proposed invasion was a ruse intended to divert British resources). On June 16, Arnold inspected West Point while on his way home to Connecticut to take care of personal business, and he sent a highly detailed report through the secret channel. When he reached Connecticut, Arnold arranged to sell his home there and began transferring assets to
London through intermediaries in New York. By early July, he was back in Philadelphia, where he wrote another secret message to Clinton on July 7, which implied that his appointment to West Point was assured and that he might even provide a "drawing of the works ... by which you might take [West Point] without loss." André returned victorious from the
Siege of Charleston on June 18, and both he and Clinton were immediately caught up in this news. Clinton was concerned that Washington's army and the French fleet would join in Rhode Island, and he again fixed on West Point as a strategic point to capture. André had spies and informers keeping track of Arnold to verify his movements. Excited by the prospects, Clinton informed his superiors of his intelligence coup but failed to respond to Arnold's July 7 letter. Arnold next wrote a series of letters to Clinton, even before he might have expected a response to the July 7 letter. In a July 11 letter, he complained that the British did not appear to trust him and threatened to break off negotiations unless progress was made. On July 12 he wrote again, making explicit the offer to surrender West Point, although his price rose to £20,000 () (in addition to indemnification for his losses), with a £1,000 ()
down payment to be delivered with the response. These letters were delivered by Samuel Wallis, another Philadelphia businessman who spied for the British, rather than by Stansbury.
Command at West Point 's house, Arnold's headquarters at West Point On August 3, 1780, Arnold obtained command of West Point. On August 15, he received a coded letter from André with Clinton's final offer: £20,000 () and no indemnification for his losses. Neither side knew for some days that the other was in agreement with that offer, due to difficulties in getting the messages across the lines. Arnold's letters continued to detail Washington's troop movements and provide information about French reinforcements that were being organized. On August 25, Shippen finally delivered to him Clinton's agreement to the terms. Arnold's command at West Point also gave him authority over the entire American-controlled Hudson River, from Albany down to the British lines outside
New York City. While en route to West Point, Arnold renewed an acquaintance with
Joshua Hett Smith, who had spied for both sides and who owned a house near the western bank of the Hudson about fifteen miles south of West Point. Once Arnold established himself at West Point, he began systematically weakening its defenses and military strength. Needed repairs of the
chain across the Hudson were never ordered. Troops were liberally distributed within Arnold's command area (but only minimally at West Point itself) or furnished to Washington on request. Arnold also peppered Washington with complaints about the lack of supplies, writing, "Everything is wanting." On August 30, Arnold sent a letter accepting Clinton's terms and proposing a meeting to André through yet another intermediary: William Heron, a member of the
Connecticut Assembly whom he thought he could trust. In an ironic twist, Heron went into New York unaware of the significance of the letter and offered his own services to the British as a spy. He then took the letter back to Connecticut, suspicious of Arnold's actions, where he delivered it to the head of the Connecticut militia. General
Samuel Holden Parsons laid it aside, seeing a letter written as a coded business discussion. Four days later, Arnold sent a coded letter with similar content to New York through the services of the wife of a
prisoner of war. Eventually, a meeting was set for September 11 near
Dobbs Ferry. This meeting was thwarted when British gunboats in the river fired on Arnold's boat, not being informed of his impending arrival.
Plot exposed in 1780 Arnold and André finally met on September 21 at the
Joshua Hett Smith House. On the morning of September 22, from their position at Teller's Point, two American rebels (under the command of Colonel
James Livingston),
John "Jack" Peterson and Moses Sherwood, fired on , the ship that was intended to carry André back to New York. This action did little damage besides giving the captain, Andrew Sutherland, a splinter in his nose—but the splinter prompted
Vulture to retreat, forcing André to return to New York overland. Arnold wrote out passes for André so that he would be able to pass through the lines, and he also gave him plans for West Point. André was captured near
Tarrytown, New York, on Saturday, September 23, by three
Westchester militiamen. They found the papers exposing the plot to capture West Point and passed them on to their superiors, but André convinced the unsuspecting Colonel
John Jameson, to whom he was delivered, to send him back to Arnold at West Point—but he never reached his destination. Major
Benjamin Tallmadge, a member of the
Culper Ring and thus a senior Continental Army
counterintelligence officer, insisted that Jameson order the prisoner to be intercepted and brought back. In a key move, Jameson reluctantly recalled the lieutenant who had been delivering André into Arnold's custody, but he then sent the same lieutenant as a messenger to notify Arnold of André's arrest. Arnold learned of André's capture on the morning of September 24 while waiting for Washington, with whom he was going to have breakfast at his headquarters in British Colonel
Beverley Robinson's former summer house on the east bank of the Hudson. Upon receiving Jameson's message, however, he learned that Jameson had sent Washington the papers which André was carrying. Arnold immediately hastened to the shore and ordered bargemen to row him downriver to where
Vulture was anchored, fleeing on it to New York City. From the ship, he wrote a letter to Washington requesting that his wife be given safe passage to her family in Philadelphia—which Washington granted. He did, however, investigate its extent, and suggested that he was willing to exchange André for Arnold during negotiations with Clinton concerning André's fate. Clinton refused this suggestion; after a military tribunal, André was
hanged at
Tappan, New York, on October 2. Washington also sent men to infiltrate New York City in an attempt to capture Arnold, which included Sergeant Major
John Champe. This plan very nearly succeeded, but Arnold changed living quarters before sailing for
Virginia in December and thus avoided capture. He justified his actions in an open letter titled "
To the Inhabitants of America," published in newspapers in October 1780. He also wrote in the letter to Washington requesting safe passage for Shippen: "Love to my country actuates my present conduct, however it may appear inconsistent to the world, who very seldom judge right of any man's actions." ==Revolutionary War (British service)==