“Davis was winning a position as a leader in the Senate. Successor to Calhoun, he had become the spokesman for southern nationalism… not independence but domination from within the Union. This movement had been given impetus by the Mexican War. Up til then the future of the country pointed north and west, but now the needle trembled and suddenly swung south. The treaty signed at Guadalupe Hidalgo brought into the Union a new southwestern domain, seemingly ripe for slavery and the southern way of life: not only Texas down to the Rio Grande, the original strip of contention, but also the vast sun-cooked area that was to become Arizona, New Mexico, Nevada, Utah, part of Colorado, and California with its new-found gold. Here was room for expansion indeed, with more to follow; for the nationalists looked forward to taking what was left of Mexico, all of Central America down to Panama, and Yucatan and Cuba by extension. Yet the North… had no intention of yielding the reigns. The South would have to fight for this… using States Rights for a spear and the Constitution for a shield. Jefferson Davis, who had formed his troops in a V at Buena Vista and continued the fight with a boot full of blood, took a position, now as then, at the apex of the wedge.”

The Civil War: A Narrative, Volume 1: Fort Sumter to Perryville (1958)