Scott's army was organized into four divisions, with Duncan's battery in Worth's 1st Division. As the American army approached Mexico City from the east, Scott ordered Worth to reconnoiter a road that would lead the Americans to attack from the south. Worth gave the task to Duncan who reported the road, "not easily obstructed or defended". Soon Scott's entire army moved by that route. At the Battle of Churubusco on August 20, 1847, Newman S. Clarke's brigade, George Cadwalader's brigade, and Duncan's battery captured the "tête de pont", a strongpoint defended by a superior force. They then helped capture the San Mateo Convent.