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 correspondence volumes of The Papers of George Washington, 1748-99, published in five series, include not only Washington's own letters and other papers but also all letters written to him. The ten-volume Colonial Series (1748-75) focuses on Washington's military service in the French and Indian War and his political and business activities before the Revolution. The massive Revolutionary War Series (1775-83) presents in documents and annotations the myriad military and political matters with which Washington dealt during the long war. The papers for his years at Mount vernon after leaving the army and before becoming president have been published in the six-volume Confederation Series (1784-88). The remaining years of Washington's life are covered in the Presidential Series (1788-97), which includes the papers of his two presidential administrations, and the four-volume Retirement Series (1797-99), which includes his correspondence after his final return to Mount Vernon.

Edward G. Lengel, ed., The Papers of George Washington: Revolutionary War Series volume 20, 8 April – 31 May 1779. Charlottesville and London: University of Virginia Press, 2010.