Inclement weather obliged Scottish-born American General Hugh Mercer to cancel a July 1776 raid on British-occupied Staten Island. Mercer's instructions to Major Thomas Knowlton specified, "Should you be successful enough to take any British troops prisoners...treat them with humanity."
Successfully conducting the raid on the night of October 15-16, 1776, Mercer informed President of the Congress, John Hancock on October 17, "The Hessian prisoners I have ordered to be treated with particular civility, that, when exchanged, they may give the most favourable report of this country...."
George Washington and the Continental Congress hoped to encourage mass desertion by the German soldiers and officers hired by the British crown to fight against American Revolutionaries. Historian David Hackett Fischer estimates that 23% of the Hessians who survived the war settled in the United States, while others returned to America with their families.
Captured Hessians were surprised by American kindness toward prisoners. After all, British officers told the Germans that Americans would not even take Hessian prisoners, but instead slaughter every Hessian who fell into American hands.
Please check Lyman H. Butterfield, "Psychological Warfare in 1776: The Jefferson-Franklin Plan to Cause Hessian Desertion," Studies of Historical Documents in the Library of the American Philosophical Society Volume 94 (June 20, 1950): 233-241; David Hackett Fischer, Washington's Crossing (New York: Oxford University Press, 2004), 378-379; Carl Berger, Broadsides and Bayonets: The Propaganda War of the American Revolution (San Rafael, California: Presidio Press, 1976).
Showing kindness to prisoners and disproving enemy propaganda became an important war aim for American Revolutionaries. For the welcome dinner Congress sponsored for Hessian prisoners captured at Trenton, New Jersey on December 25-26, 1776, please visit the post "Parties for Prisoners."