1780 - September 25 - Benedict Arnold's plans to cede West Point to the British discovered.

On September 25, 1780, one of the most infamous incidents in American Revolutionary history occurred: the discovery of Benedict Arnold's plot to betray West Point to the British. Arnold, a former American general, had become disillusioned with the Revolutionary cause and sought personal gain by offering to hand over the strategically important fort to the British. His plan was to weaken the American position and secure a high-ranking position in the British army.

However, his scheme was foiled when British Major John Andre, who was carrying documents related to the plot, was captured by American forces. This led to the exposure of Arnold's treachery. Arnold managed to escape to the British lines, but his name became synonymous with betrayal in American history.