It was, of course, not the first war to be waged on the grounds that it would serve a humanitarian purpose. The United States’ first full-scale invasion of a nation state came more than a century ago, with the Mexican-American War fought from 1846 to 1848. The war resulted in vast territorial gains for the United States that included all or parts of California, Arizona, Nevada, New Mexico, Colorado, Utah, Wyoming, Texas, Kansas and Oklahoma. Mexico lost 55 percent of its claimed territory.
Advocates for the invasion emphasized the Mexican people’s need for U.S. protection against powerful Indigenous nations, and argued that the United Stateswould secure and develop Mexico’s northern peripheries. By framing the invasion as somehow serving Mexicans’ needs, the United States established a rhetoric of protection and relief that would go on to justify many subsequent invasions.
In the first half of the 19th century, Indigenous people, including Comanches, Kiowas and Apaches, launched raids from the Southern Plains and what is now the Southwest of the United States deep into Mexico to obtain herd animals for subsistence and trade. These raids were devastating and costly, and Northern Mexico’s economy and population stagnated. The region’s states petitioned Mexico City for monetary and military aid — but indebted from its war for independence and mired in political instability, the newly established Mexican government had little to offer.
The United States, meanwhile, was expanding westward and claiming ever more territory. Under the widely accepted 19th century doctrine expressed by a newspaper editor in 1845, many Americans believed it was “by right of our manifest destiny to overspread and to possess the whole of the continent.” This belief led the United States to offer to purchase Mexican California, which at the time included all or part of what is now Nevada, Arizona, Utah, Wyoming and Colorado.
When the Mexican government refused to sell, the United States began to take it. For example, the Anglo American immigrant population in Texas had declared independence from Mexico in 1836 and the United States then annexed this land in 1845.
When President James K. Polk entered office in March 1845, he embraced Texas annexation. Intending to further expand the United States, Polk sought to test Mexico by sending U.S. troops across the Nueces River, the historical boundary of Texas, southward toward the Rio Grande. Polk insisted the Rio Grande was the actual boundary between the two countries — even though the people residing between the two rivers considered themselves part of Mexico.
After Mexican troops attacked American soldiers along the northern bank of the Rio Grande, Polk asserted that “Mexico has passed the boundary of the United States, has invaded our territory, and shed American blood upon the American soil.” He urged Congress to declare war.
Some Americans, including Ralph Waldo Emerson, Henry David Thoreau and Abraham Lincoln, resisted the slide into war. In his first term in Congress, Lincoln called the war a threat to the nation’s republican values that would result in slavery spreading westward, and questioned Polk’s claim that Mexicans had spilled American blood on U.S. soil. Many believed that Polk had provoked hostilities as a pretext to expand the nation to the Pacific Ocean.
But the voices of those clamoring for war, including journalists and travel literature, drowned out the opposition. They framed the war as a way to alleviate the suffering of Mexican people, enhance industry and fuel colonial settlement.
Sen. Robert Walker (D-Miss.) helped establish these tropes in 1836, declaring that Anglo Americans were invited to settle in Texas to “defend the Mexicans against the then frequent incursions of a savage foe.” A myth emerged in American political and popular discourse that Anglo Texans were arising to defend and protect Mexican people from raids by Indigenous groups.
Other politicians insisted that Indigenous nations could not be allowed to hinder Mexico’s commerce, pointing to U.S. intervention as a solution. Throughout the 1830s and 1840s, newspapers from Louisiana to New England detailed the human suffering from Indigenous raids in Mexican ranches, towns and cities.
In reality, these conflicts between Mexicans and Indigenous groups were hard fought, included significant casualties on all sides and resulted in counterattacks by both Mexicans and Indigenous people. But travel writers regularly portrayed Mexicans as helpless and in need of American aid. Waddy Thompson, the U.S. ambassador to Mexico from 1842 to 1844, wrote in his 1846 “Recollections of Mexico”: “I do not think that the Mexican men have much more physical strength than our women,” while insisting in the same text that Indigenous forces would be no match for Anglo Americans if the United States were to storm Mexico.
When the United States — with a growing economy and a population of 20 million vs. Mexico’s 7 million — invaded Mexico, it attacked on multiple fronts. By sea, 70 ships took the port of Veracruz and troops marched on to Mexico City. The Mexican-American War resulted in one of the highest casualty rates in American history. Of the 79,000 American soldiers who served, more than 16 percent died in battle or from disease. At over 8 percent, the Mexican-American War also had the highest desertion rate of U.S. troops of any war. Still, the better-trained and better-equipped U.S. forces took the Mexican capital.
The 1848 Treaty of Guadalupe Hidalgo that ended the war stated, with the open bigotry of the era, that the lands Mexico was ceding claims to were “occupied by savage tribes, who will hereafter be under the exclusive control of the Government of the United States, and whose incursions within the territory of Mexico would be prejudicial in the extreme.” The treaty said that such “incursions” would be “forcibly restrained by the Government of the United States.”
Indigenous people were, of course, not included in treaty negotiations that had enormous implications for their lives and sovereignty.
In the end, life was not better for Mexicans. At least 25,000 people, mainly civilians, died during the war. Having defeated Mexico and taken more than half of its claimed territory, U.S. leaders underestimated the military capabilities of the Indigenous populations who actually controlled the vast lands Mexico ceded on paper. North of the newly drawn border, Mexican Americans, whom the Treaty of Guadalupe Hidalgo made U.S. citizens, and Navajos persistently preyed upon one another through raids and counterraids in New Mexico. Plains Indigenous people continued to attack Mexican American settlements in Central and South Texas. In fact, in what was now northern Mexico, raids intensified as Indigenous people freely journeyed south from territory that the United States took from Mexico but which was actually controlled by Indigenous people.
The United States could not live up to its treaty obligations or protect its own citizens from the violence that reverberated after the Mexican-American War. The nation was unable to mount sufficient force across a vast region to subdue independent Indigenous populations that were still fighting to maintain their homelands against colonization. Hostilities in the Southwest remained until almost the mid-1920s, and sovereignty disputes continue today.
A century and a half later, the United States government similarly misjudged its capabilities and underestimated the costs of invading and redeveloping Afghanistan. The Taliban, which had hosted al-Qaeda, while pushed out of formal power by a coalition of forces in 2001, has now retaken control of Afghanistan. The government that the United States fought for almost two decades to prop up has crumbled.
Although Americans used different language to justify the very different invasions of Mexico in 1846 and Afghanistan in 2001, both wars were underwritten by the willful belief in the American ability to develop invaded lands under its world views while “protecting” and “rescuing” invaded peoples. Now that the Afghanistan war has ended, Americans must consider whether this unfounded faith will remain at the heart of how we engage the world, or if we will consider the often-catastrophic results of U.S. invasions.