Enraged by his treatment in Philadelphia, General Arnold resigned his command there in March 1779. Pursuant to the secret communications with the British, he sought and obtained the command of West Point, a critical American defense post in the highlands of the Hudson River. Peggy and their infant son Edward Shippen Arnold (born 19 Mar 1780) joined him there in a home on the Hudson two miles south of West Point. General Arnold systematically weakened the defenses of West Point with the intent of making it easier for the British to capture.