This caused Polk to harden his position on Mexico, and he ordered an American landing at Veracruz, the most important Mexican port on the Gulf of Mexico. From there, troops were to march through Mexico's heartland to Mexico City, which it was hoped would end the war. Continuing to advance in northeast Mexico, Taylor defeated a Mexican army led by Ampudia in the September 1846 Battle of Monterrey, but allowed Ampudia's forces to withdraw from the town, much to Polk's consternation. Polk believed Taylor had not aggressively pursued the enemy and offered command of the Veracruz expedition to Scott.