In March 1847, Polk learned that Taylor had ignored orders and had continued to march south, capturing the northern Mexican town of Saltillo. Taylor's army had repulsed a larger Mexican force, led by Santa Anna, in the February 1847 Battle of Buena Vista. Taylor won acclaim for the result of the battle, but the theater remained inconclusive. Rather than pursuing Santa Anna's forces, Taylor withdrew back to Monterrey. Meanwhile, Scott landed in Veracruz and quickly won control of the city. Following the capture of Veracruz, Polk dispatched Nicholas Trist, Buchanan's chief clerk, to negotiate a peace treaty with Mexican leaders. Trist was ordered to seek the cession of Alta California, New Mexico, and Baja California, recognition of the Rio Grande as the southern border of Texas, and American access across the Isthmus of Tehuantepec.