In 1846, the U.S. planned to launch a three-pronged attack on Mexico and force negotiations. Stephen Kearny’s army marched for California, while Taylor's army pushed south of the Rio Grande. Wool’s Army of the Central was to attack Chihuahua. Outside San Antonio, Wool assembled his forces, mostly volunteers from Arkansas, Indiana and Illinois. After crossing the Rio Grande at Presidio (near Del Rio, Texas), Wool issued a statement to his troops saying:

"All depredations on the persons or property of the people of the country are strictly forbidden; and every soldier or follower of the camp, who may so far forget his duty as to violate these injunctions will be severely punished."

Wool's army marched 500 brutal miles through Mexico to Monclova and Parras. By the time they reached Parras, their mission to Chihuahua was unnecessary. In December 1846, Wool’s army was summoned to join Taylor's forces south of Saltillo.