(April 1847), confrontation at a mountain pass about 60 miles (97 km) northwest of Veracruz, Mex., where the U.S. Army under General Winfield Scott (Scott, Winfield) first met serious resistance in the Mexican War. Advancing to the interior, Scott's 8,500 men reached Plan del Río, a few miles from Cerro Gordo, where they met a Mexican force of 12,000 men under General Antonio López de Santa Anna (Santa Anna, Antonio López de) entrenched in the pass. A flanking maneuver to gain the enemy rear, suggested and guided by Captain Robert E. Lee (later commanding general of the Confederate Army), was in progress when fighting began on the front, and the Mexicans broke. Santa Anna escaped, leaving about 1,130 casualties and about 3,000 prisoners. The American loss was 431, including 63 dead. Scott moved on to Puebla, the second largest city of Mexico, and later to Mexico City.