Manson served under various enlistments from July 1776 to January 1778. He reenlisted in what was called the "Flying Camp" under Colonel William Cosby. He aided in building Fort Lee and retreated when Fort Washington was taken. Manson served as an aide to General George Washington and held the rank of private. He was with Washington on the night of December 25–26, 1776 when he crossed the Delaware River.