Volume 20 of the Revolutionary War Series covers 8 April to 31 May 1779. As it begins, Washington is gathering intelligence in preparation for a summer expedition against the Iroquois Confederacy. After considering various intelligence reports compiled with the help of scouts and spies, he issued comprehensive orders to the expedition's commander, Major General John Sullivan, laying out his plan of campaign. At the same time, Washington viewed with concern the worsening situation in the south, where the British had captured Savannah, Georgia, and were pressuring Charleston, South Carolina. His attempts to dispatch reinforcements southward were interrupted, however, by a devastating British raid on Portsmouth, Virginia, in early May. Washington's development of his espionage network in New York City reaped dividends later that month when one of his spies--a double agent--alerted him ahead of time of a British attack up the Hudson River toward West Point. Thanks to this timely intelligence, Washington prepared his troop dispositions and defenses in advance; and although the British managed to capture King's Ferry, New York, at the end of May, they posed no threat to West Point. Beneath the surface, however, a new and potentially more dangerous threat was brewing: Major General Benedict Arnold, enraged at Washington's inability to clear up Arnold's dispute with Congress and the Government of Pennsylvania, initiated secret contacts with the British. The publication of this volume has been supported by a grant from the National Historical Publications and Records Commission.