The War with Mexico (1846–1848) was such a dramatic victory for the United States that it led many citizens to believe there was nothing their nation could not achieve. Even the Duke of Wellington, the victor over Napoleon at the Battle of Waterloo, freely confessed his opinion that General Winfield Scott was the greatest living soldier.

Politicians like Henry Clay, Daniel Webster, and John C. Calhoun witnessed the conclusion of the War with Mexico, but it was their last hurrah. Such men had either retired from Congress or were now in the grave. They were replaced by a more aggressively sectional group of men in Congress, persons such as Charles Sumner of Massachusetts and Louis T. Wigfall of Texas. Buoyed by their country’s victory in the Mexican War, believing in Manifest Destiny, this new generation of politicians did not fully realize how dangerous their sectional politics were; if a new war were to commence, it would be fought between the sections of the young nation, rather than against a foreign foe.