During the war, Benedict Arnold proved himself a brave and skillful leader, helping Ethan Allen’s troops capture Fort Ticonderoga in 1775 and then participating in the unsuccessful attack on British Quebec later that year, which earned him a promotion to brigadier general. Arnold distinguished himself in campaigns at Lake Champlain, Ridgefield and Saratoga, and gained the support of George Washington. However, Arnold had enemies within the military and in 1777, five men of lesser rank were promoted over him. Over the course of the next few years, Arnold married for a second time and he and his new wife lived a lavish lifestyle in Philadelphia, accumulating substantial debt. The debt and the resentment Arnold felt over not being promoted faster were motivating factors in his choice to become a turncoat.
In 1780, Arnold was given command of West Point, an American fort on the Hudson River in New York (and future home of the U.S. military academy, established in 1802). Arnold contacted Sir Henry Clinton, head of the British forces, and proposed handing over West Point and his men. On September 21 of that year, Arnold met with Major John Andre and made his traitorous pact. However, the conspiracy was uncovered and Andre was captured and executed. Arnold, the former American patriot, fled to the enemy side and went on to lead British troops in Virginia and Connecticut. He later moved to England, though he never received all of what he’d been promised by the British. He died in London on June 14, 1801.
– History.com Staff