After crossing the Rio Grande, in September Taylor inflicted heavy casualties upon the Mexicans at the Battle of Monterrey, and captured that city in three days, despite its impregnable repute. Taylor was criticized for signing a "liberal" truce, rather than pressing for a large-scale surrender. Polk had hoped that the occupation of Northern Mexico would induce the Mexicans to sell Alta California and New Mexico, but the Mexicans remained unwilling to part with so much territory. Polk sent an army under the command of Winfield Scott to besiege Veracruz, an important Mexican port city, while Taylor was ordered to remain near Monterrey. Many of Taylor's experienced soldiers were placed under the command of Scott, leaving Taylor with a smaller and less effective force. Mexican General Antonio López de Santa Anna intercepted a letter from Scott regarding Taylor's smaller force, and he moved north, intent on destroying Taylor's force before confronting Scott's army.