September 14, 1847 - October 12, 1847
The U.S.-Mexico War did not end with the fall of Mexico City in mid-September, 1847. Having renounced the presidency, Santa Anna gathered what remained of his defeated army and marched west, toward Puebla, in a last-ditch effort to cut off Scott's supply lines from the coast.
U.S. troops had occupied Puebla since May. When Winfield Scott began his march into the Valley of Mexico in August, he left behind a garrison of 400 men under Colonel Thomas Childs to guard the National Road that connected the capital to Vera Cruz. Soon after Scott left the city, Mexican forces and local militia led by General Joaquín Rea began harassing the garrison, driving off the quartermaster's mule herd, destroying bakeries that supplied the garrison with bread, and destroying the aqueduct that provided a water supply for the city.
On September 14, as Winfield Scott marched into Mexico City in triumph, the siege of Puebla began. Rea's forces attacked several fortified positions held by U.S. troops, issuing a demand that Childs surrender unconditionally, which was refused.
On September 22, Santa Anna arrived from Mexico City at the head of his battered army to take command of the siege. Learning that a U.S. relief column under General Joseph Lane was coming up the National Road from Vera Cruz, Santa Ann moved his troops to Huamantla, a town northeast of Puebla, to intercept it.
Lane's force gathered strength during its march from the coast, picking up additional troops from garrisons in towns along the National Road, and by the time it reached Huamantla, had swelled to 3,000. On October 9 Lane attacked the town, ordering Captain Samuel H. Walker's company of U.S. Mounted Rifles to lead the advance. As the discouraged remnants of the Mexican army were driven back, Walker was killed by sniper fire. The death of the popular officer enraged Lane's men, who sacked the town in retaliation.
The following day Lane pressed on to Puebla, where U.S. troops defeated Rea's force on the outskirts of the city, bringing the siege to an end on October 12.