The U.S. invasion of Mexico in 1846 is best known to Texans as the conflict that ensured that our state would remain part of the United States and established the Rio Grande as its southern border. It was also the first American war for territory waged against another republic—and the first that a significant number of Americans felt ashamed of. Ulysses S. Grant, who as a junior officer witnessed countless rapes, murders, and other atrocities committed by U.S. soldiers against the Mexican population, felt remorse about his role in it for decades. “I do not think there was ever a more wicked war than that waged by the United States on Mexico,” he wrote in 1879. “I thought so at the time, when I was a youngster, only I had not moral courage enough to resign.”

Amy S. Greenberg’s top-down history, A Wicked War: Polk, Clay, Lincoln, and the 1846 U.S. Invasion of Mexico (Knopf), chronicles the lives of two men who did muster up the courage to speak out against what they saw as President James Polk’s blatant land grab: U.S. presidential candidate Henry Clay and freshman congressman Abraham Lincoln, whose highly publicized declarations served as a rallying point that galvanized peace activists throughout the country. The war was, in Greenberg’s telling, the first foreign conflict in American history that was curtailed by widespread domestic protests and Congressional opposition—a precursor, perhaps, of the failed American engagement in Vietnam (Greenberg, a professor of history and women’s studies at Penn State University, doesn’t draw this connection). Her book, though, never quite nails the case that her central protagonists were as influential as she claims.

Clay and Lincoln’s most prominent allies in their fight were the abolitionists, who opposed the war because they believed it would bring more slave territory to the Union—the same reason they had opposed the annexation of Texas in 1845, which remained a major point of contention between the United States and Mexico. Whether extending slavery was, in fact, Polk’s intent (he was a lifelong slaveholder) is still a source of debate among historians. But he certainly intended to extend the U.S. empire to the Pacific coast. Hoping to provoke a war that would allow him to do that, in February 1846 he ordered U.S. troops stationed in Corpus Christi to advance into disputed territory south of the Nueces River. Two months later, when Mexican troops under the command of General Mariano Arista surrounded a U.S. scouting party near the Rio Grande and killed numerous American soldiers, Polk finally had the pretext he needed to begin an invasion he had been calling for since the beginning of his presidency. In May he asked Congress to officially declare war against Mexico.

U.S. forces launched a three-pronged offensive from Texas, California, and Veracruz against General Antonio López de Santa Anna’s forces. The U.S. won most of the major battles and captured Mexico City. But the conflict had been extremely bloody and costly. U.S. casualty rates were, even to this day, the highest of any American war: approximately 17 percent of the total U.S. forces, more than 13,000 American soldiers. About 25,000 Mexicans, mostly civilians, perished as well. The Treaty of Guadalupe Hidalgo, signed on February 2, 1848, forced the Mexican government to give away 525,000 square miles of its territory in exchange for $15 million.

Many American war hawks called for the annexation of all of Mexico. Polk wanted to expropriate nearly two thirds of the country. But in A Wicked War, Greenberg argues that Clay and Lincoln’s staunch opposition moved public opinion and Congressional opinion so sharply that Polk had to settle for half. Mexico had to cede only what is now Texas, California, New Mexico, Colorado, Nevada, Utah, Oklahoma, Kansas, and most of Arizona.

But how much credit can we really give to Clay, Lincoln, and their allies for this dubious victory? Compared with, say, the Civil War, World War II, or the Mexican Revolution, relatively little has been written about the U.S.-Mexican War. But a few historians of the war who preceded Greenberg have convincingly argued that it was primarily Mexican resistance, rather than domestic opposition, that compelled Polk to pull out his troops before attaining all of his territorial objectives. Irving Levinson’s Wars Within War: Mexican Guerrillas, Domestic Elites, and the United States of America, 1846–1848, which was published by Texas Christian University Press in 2005, thoroughly documents how the armed peasant movements that had once fought against the Mexican government began to turn their weapons against the U.S. occupation forces during the course of the war. 

Levinson’s book provides evidence in support of an idea first proposed by Ramón Alcaraz, a Mexican army officer and historian who wrote several books on the U.S.-Mexican War in the nineteenth century. Alcaraz concluded that a protracted large-scale insurgency throughout Mexico would have ultimately forced the United States to withdraw its troops without a treaty. Indeed, Polk’s generals understood that a drawn-out struggle against insurgents would have  been even more costly than a fight against regular troops. U.S. military leaders were particularly worried about scenarios in which Mexicans and indigenous groups joined forces, such as the February 1848 attack on two hundred U.S. troops by five hundred New Mexicans, Apache, and Comanche near El Paso.

Levinson was not the first modern historian to question the central role of American peace activists in bringing the war to a close. In his 1973 book, Mr. Polk’s War: American Opposition and Dissent, 1846–1848, John Schroeder argued that the antiwar movement “had little effect on the war’s duration, outcome, or final terms.” (One wonders how much his thesis was influenced by the Vietnam War, which was raging as he wrote and which was the subject of domestic protests that were regarded as more effective than they likely were.) Greenberg argues that Schroeder underestimated the impact of American opposition during the U.S.-Mexican War, but her failure to give the Mexican resistance its due hobbles her argument.

That’s not to say that A Wicked War is without its merits. It’s an easy-to-read scholarly work that offers intriguing insights about the social history of elite American society during the 1840’s. It sheds new light on how the experiences of Clay, Lincoln, and other prominent figures during the war shaped American identity and patriotism. One wishes it possessed more of the analytical sophistication of her previous book, Manifest Manhood and the Antebellum American Empire, which skillfully explored how nineteenth-century notions of what she calls “restrained manhood” and “martial manhood” played out in American expansionism. But the major shortcoming of A Wicked War is that it almost exclusively depends on evidence from U.S. historical sources—from archival collections to newspapers—largely ignoring the documents available on the other side of the border. Today few historians would write about the Civil War, for example, after looking only at historical evidence produced by the Union. The U.S.-Mexican War begs for a transnational approach.

A Wicked War is certainly more nuanced than the traditional accounts of American military superiority and is generally sympathetic to the Mexicans. But they mostly play the part of the silent victims. Unlike the determined Americans in Greenberg’s book, the people south of the border don’t get the chance to be complicated or influential. They’re portrayed as little more than pawns in a wicked game.