Final answer:
Winfield Scott was a significant military leader who captured Mexico City during the Mexican-American War, cementing his status as a military hero.
Step-by-step explanation:
Winfield Scott was a prominent military figure in the history of the United States. He led the Army of the South and was considered a potential competitor for the presidency due to his military successes. The decision by President Polk to assign Scott the crucial campaign to seize Mexico City during the Mexican-American War was strategic to avoid elevating another popular military leader, Taylor, who was affectionately known as "Old Rough and Ready." Scott's successful capture of Mexico City indeed turned him into a military hero.