Taylor became a military hero due to several victories during the Mexican–American War, which began in 1846. Now a general, Taylor defeated Mexican forces at Palo Alto and then at Resaca de la Palma. Taylor and the Americans had superior artillery fire and were able to inflict many more casualties. He was awarded two gold medals for these victories.

Taylor further entrenched himself into the country’s consciousness as a hero after he led his troops to victory at Monterey. President Polk, a diehard Democrat, became displeased with Taylor, whom he saw as a possible Whig candidate. Polk also believed that Taylor had granted too generous terms to the Mexicans following the taking of Monterrey. Polk then replaced Taylor with General Winfield Scott on a mission to march to Mexico City.

Taylor vowed not to resign and instead did something unexpected against presidential orders. With a much smaller force he engaged the Mexicans at the Battle of Buena Vista in February 1847. The Mexican leader Santa Anna could not defeat Taylor’s much smaller military force. This battle ensured that Taylor had presidential possibilities.