From the outbreak of the Revolution Sheftall was prominently identified with the Patriot cause, vocally opposing the 1765 Stamp Act imposed by the British Parliament. He became chairman of "the Parochial Committee," organized to regulate the internal affairs of Savannah, and composed of patriots opposed to the royal government; his appointment has been taken by some to indicate the level of high standing Sheftall enjoyed among both Jews and Gentiles. In 1777 Sheftall was appointed commissary-general to the troops of Georgia and to the Continental troops also; in October of the following year he became "Deputy Commissary of Issues in South Carolina and Georgia"; and he figured as a staff-officer in the Continental line of the Georgia brigade during the war. Major General Robert Howe gave him the rank of colonel as a result. Sheftall appointed his son Sheftall as his assistant. When the British attacked Savannah in late 1778, Sheftall not only took an active part in its defense, but he also advanced considerable sums of money (including loans) for the American cause. After the city had been taken, he and his son were captured by the British. As a consequence of refusing to renounce his loyalty to the Patriot cause, the British took him to the prison ship "Nancy" with his son Sheftall and kept him there as a prisoner of war.