On August 31, a British fleet under Thomas Graves left New York for Yorktown. After landing troops and munitions for the besiegers on August 30, de Grasse had remained in Chesapeake Bay and intercepted him on September 5; although the Battle of the Chesapeake was indecisive in terms of losses, Graves was forced to retreat, leaving Cornwallis isolated. An attempted breakout over the York River at Gloucester Point failed due to bad weather. Under heavy bombardment with dwindling supplies, Cornwallis felt his situation was hopeless and on October 16 sent emissaries to Washington to negotiate surrender; after twelve hours of negotiations, these were finalized the next day.