September, 1846 - February, 1847
Both sides regrouped following the surrender of Ampudia's Army of the North at Monterrey in September, 1846. According to the terms of the agreement signed by Taylor and Ampudia, the Army of the North was allowed to evacuate the city, taking with it some of its arms and equipment. Ampudia's troops would spend the next several months in San Luis Potosi, headquarters of the Mexican army's Third Division.
General Zachary Taylor, meanwhile, took steps to consolidate the Army of Occupation's control of northern Mexico. He occupied Saltillo in mid-November, and soon afterward garrisoned the coastal city of Tampico. In December, U.S. forces occupied the towns of Parras and Victoria. In January, however, Taylor's army was sharply reduced when most of his regulars and some volunteers were ordered to join Major General Winfield Scott for the invasion of Vera Cruz. By early February, Taylor's remaining troops were concentrated in the Saltillo area. To strengthen what remained of the Army of Occupation, Taylor ordered General John Wool, commander of the Center Division, to join him in Saltillo. Mustered in San Antonio, Wool's division had originally been intended to take part in the advance on Chihuahua. By year's end Wool's force had taken control of Monclova and Parras before linking up with Taylor's army. Now numbering approximately 11,000, most of whom were volunteers, Taylor's force would meet Santa Anna at Buena Vista in February, 1847.