In late August 1780, Gen. George Washington was buoyed by expectations that French reinforcements would participate in an attack on New York City and that a southern army was poised to advance through South Carolina and possibly regain Charleston. News soon reached him that a key division was delayed in France and that units under Maj. Gen. Horatio Gates had been scattered near Camden, S.C. In response to these crises, Washington dismissed northern militia to conserve supplies, directed additional forces to the southern department, and selected Maj. Gen. Nathanael Greene to replace Gates. In a dramatic turn of events, Washington learned of the defection of Maj. Gen. Benedict Arnold—who had plotted with British adjutant general John André to betray West Point—and, acting decisively, concentrated his troops and rebuffed British appeals to spare the captured André (who was hanged as a spy), ensuring "the rescue of the Post & Garrison of West point from Arnolds villainous perfidy.