In April 1846, the army of General Zachary Taylor, which President Polk had sent to the Rio Grande River, clashed with a Mexican force sent to drive the Americans away. Soon after, Taylor fought two brief battles (Palo Alto and Resaca de la Palma) with the Mexicans, driving them across the Rio Grande. After a pause of a few months, the two armies clashed again at Monterrey. Meanwhile, an old “friend” re-entered the story.