July 15, 1780: Benedict Arnold's encoded letter to John André in which he offered to sell West Point to the British.
Embittered by the lack of recognition he had received for his accomplishments, in debt, and humiliated, Benedict Arnold offered to sell West Point, what would have been a key tactical accomplishment to have control over, to the British. While in transit, however, the documents were discovered, and Arnold, unsuccessful, fled to England.