April 17, 1847 - April 18, 1847
In April, Santa Anna moved to block the U.S. Army's advance from the coast, digging in along the National Road in a narrow mountain pass east of Jalapa.
Santa Anna had chosen what appeared to be a formidable defensive position. After a thorough reconnaissance of the area, however, Robert E. Lee, then a captain in the U.S. Army Corps of Engineers, concluded that a path could be cut through the mountains, enabling Scott to throw his troops and artillery against a weakly defended left flank. On April 17 U.S. troops seized one of the outlying foothills on the Mexican left, and the following morning stormed Telegraph Hill (El Telégrafo), the linchpin of the Mexican defensive line. Although Santa Anna learned of Scott's plan from an American deserter, by the time he realized that the primary U.S. assault would not come from the main road, it was too late to redeploy his forces. The battle soon turned into a rout as Mexican troops retreated in confusion and disorder toward Jalapa.
The way to Mexico City now lay open to Winfield Scott and the U.S. army.