Fault Lines: The United States–Mexican War Reconsidered and Remembered

From 1845 to 1848, a surge of territorial expansion took the nation to the Pacific Coast and made it a true continental empire. The rhetoric of Manifest Destiny, which had begun to take shape in the 1820s, became florid, exaggerated, and protean. John L. O’Sullivan, editor of the United States Magazine and Democratic Review, wrote in 1845 that the nation’s destiny—now quite manifest to him and other expansionists—was “to overspread and to possess the whole of the continent which Providence has given us for the development of the great experiment of liberty and federative self-government entrusted to us.”¹ O’Sullivan’s altruistic sentiments masked a darker and harsher reality. The supposed natural, predestined right to expand would come at the expense of other peoples—Native Americans and Mexicans in the Southwest. Moreover the Mexican War, which grew out of these racist assumptions and made real these territorial designs, would transform political culture, make salient sectional fault lines, and give a sectional cast to the expansionist impulse in the 1850s. Ironically and at the same time, as Amy Greenberg argues, racism would be an element in antiwar sentiment during the war and remain central to and “continue to shape anti-imperialism for the rest of the century” (p. 263). In Mexico, the legacy of the war became essential to the stabilization and empowerment of the central government. Throughout the nineteenth and twentieth centuries, Mexico’s leaders, Michael Scott Van Wagenen maintains, “were able to draw from the memory of their battlefield losses to promote national unity and foster support for political reform” (p. 6).

Greenberg structures her insightful, accessible, thoughtful, and thought-provoking narrative around the personal and public lives of James K. Polk, Henry Clay, Nicolas Trist, and two Illinois Whigs, John J. Hardin and Abraham Lincoln. Central to her analysis are the intertwined questions of conscience and morality. They operate both at a personal level and on a national scale. Polk, whose bellicose diplomacy provoked the conflict with Mexico in order to realize his continental empire, steadfastly viewed the war as a patriotic mission. By turns impatient, given to intrigue, sober-minded, disciplined, and as politically willful as he was disingenuous, the president would dictate to Mexico and bend that nation to his will as he did his slaves. To his mind, domination of the strong over the weak and white over black was as much a part of God’s plan as was the Providential directive to overspread the continent. Greenberg contends that Polk’s war was a watershed in diplomacy, making the United States an international power. But it was more. “His was the first American War against a neighboring republic, the first started with a presidential lie, and the first that a large number of American people felt guilty about” (p. 268). Polk, however, died with a clear conscience. More is the pity.

Clay, who had lost to Polk in the 1844 presidential contest that turned largely, though not exclusively, on the issue of Texas annexation and more generally on territorial expansion, is a pivotal and tragic figure. He lost his son Henry Clay Jr., “the pride and hope” of the family, at the Battle of Buena Vista. Clay was devastated. Determined to find some private consolation and to make sense of his son’s death, Clay came out publicly and forcefully against the war in a widely publicized speech in November 1847. Placing principle above politics, Clay condemned Polk’s “unnecessary” war of “offensive aggression.” He regretted that the president’s policies had damaged—perhaps irreparably—the nation’s international character. And he rejected any desire to acquire territory “for...