U.S. victory at a hamlet southwest of Mexico City, with which on Aug. 19–20, 1847, the army of Maj. Gen. Winfield Scott opened the final campaign of the Mexican War. Finding the road from Acapulco to Mexico City blocked by units of Gen. Antonio López de Santa Anna's army, Scott took the difficult road across the lava beds south of Lake Chalco. That route was held by Gen. Gabriel Valencia, who occupied the hill of Padierna, north of Contreras. On August 19 in an engagement lasting less than 20 minutes, Scott drove Valencia from Contreras and gained control of several roads leading to Mexico City. Before pushing on to the capital, he turned to attack the Mexicans on the Acapulco road and on August 20 captured Santa Anna's principal army at Churubusco.