War on the Border
Lessons from the Mexican-American war.


On July 7, 1846, a contingent of Marines raised the American flag over Monterey, California, to mark a proclamation by U.S. consul Thomas Larkin that the territory was being annexed as a consequence of the war with Mexico. Much of the future state had already been taken from Mexico’s nominal control by an uprising of American settlers under the Bear Flag.

Victory in the Mexican War meant that the country gained Texas, California, and everything in between, comprising most of what is now New Mexico, Arizona, Nevada, Utah, Colorado, and Wyoming. Next to the War of Independence and the Civil War, the Mexican War was the most important conflict laying the foundations of the United States as the power that it is today. Yet the war was controversial at the time, and the arguments and political maneuvering surrounding it still echo in debates over two of the most pressing issues today: immigration policy and presidential war powers.

Mexican textbooks claim that the American southwest was “stolen” and will someday be regained. Radical elements in the movement championing an “open border” between the U.S. and Mexico hope to someday fulfill this irredentist ambition. They see a mass movement of people overwhelming the “anglo” population of the border states.

This is ironic, because it was the influx of American settlers into California and Texas that lost these territories to Mexico in the first place. From 1824 to 1830, promises of cheap land and tax breaks attracted Americans to settle in Texas on the condition they become Catholic and swear allegiance to Mexico. But the number of American colonists eventually began to alarm the Mexican government, which in 1830 prohibited future immigration and tried to coax its own people to move north. Still, illegal American farmers, ranchers, and merchants kept coming. In response to the repressive dictatorship of Antonio Lopez Santa Anna, these Texicans revolted in 1835. They declared their independence a year later and established it on the battlefield.

The Texans wanted to rejoin their homeland, but domestic U.S. politics delayed this development for a decade. The Democrats favored bringing Texas into the union. This had been one of the priorities of Andrew Jackson and his protégé Sam Houston. But the Whigs, centered in New England, opposed what they misperceived primarily as a new territory of slave-owners. The larger benefits of national enlargement eventually prevailed in regard to Texas, but the slavery issue continued to be used in partisan propaganda opposing further expansion during the Mexican War.

The proximate cause of the Mexican War was a dispute about where to draw the international border after Texas joined the United States in 1845. Texas had claimed the Rio Grande River, but neither this line nor the independence of Texas had yet been recognized by the Mexican government. President James Polk, a Democrat and our most underrated president, tried to buy the disputed area, as well as California and New Mexico. This was how Thomas Jefferson had obtained the vast Louisiana Purchase from Napoleon, who knew he couldn’t hold the territory and needed the money. The Mexican government seemed in the same plight, bankrupt and on the brink of civil war. In December 1845, President Jose Herrera told his state governors that Texas had no value because not enough Mexicans could be persuaded to move there to hold it. The same could have been said about California and the southwest.

There was a plot to install a Spanish nobleman as monarch to restore order, and a military coup overthrew Herrera before an agreement could be reached on a land sale. A war for the borderlands then began, followed shortly by another coup that brought Santa Anna back to power. This represented a swing to the right in Mexican politics, motivated by the desire to resist American demands. There was wild talk about not only retaking Texas, but also marching on New Orleans and sending fleets of privateers against U.S. trade.

With diplomacy failing, Polk had sent 4,000 soldiers under General Zachary Taylor to enforce the boundary claim against Mexico. On April 25, 1846, American soldiers were attacked north of the Rio Grande by Mexican troops. Polk asked Congress to declare war on May 12, the day after word of the battle reached Washington. The House vote was a comfortable 174–14, but the Senate tally was much narrower — it passed the war proclamation by only one vote.

The war was initially very popular in America. Some 200,000 men rushed to join the Army in response to a call for 50,000 volunteers (when war was declared, the U.S. Army had only 10,000 men, a much smaller force than the standing Mexican army). In Tennessee, from where many of the Texas settlers had come, so many wanted to join that lots had to be drawn. The winners got to enlist. The name of the University of Tennessee’s athletic teams  –”The Volunteers” — is linked to this episode.

Still, many Whigs were against the expansionism of the war, and some Democrats were concerned about presidential power. The Whigs were willing to accept Mexico’s claims to the border, and they denounced Polk for sending U.S. troops into harm’s way to contest the issue. The young Congressman Abraham Lincoln introduced the infamous “spot resolution” demanding that Polk prove that the “spot” in Texas where American blood had been spilled was legitimate U.S. territory. (Fortunately, Lincoln matured into a stubborn president who would not accept anything less than victory in the Civil War, and would do whatever was needed to prevail. Even during the Mexican War, he and most other Whigs still voted the money and supplies to support the troops in the field despite their dissent over how the conflict started.)

Democratic senator John C. Calhoun of South Carolina, a defender of states’ rights and slavery, believed Polk had acted in an offensive and unconstitutional way, without prior congressional authorization. Calhoun’s opposition to the war made for an uneasy alliance with the anti-slavery Whigs who saw the war as a southern plot. Democratic senator Thomas Hart Benton of Missouri agreed, claiming “Never have the men at the head of government . . . [been] more addicted to intrigue.” Whig Rep. Joshua Giddings of Ohio denounced “sending an army to invade a neighboring nation, to shoot down our brethren of Mexico” and claimed that “on the day of final retribution, the blood of our slaughtered countrymen” would be on Polk’s hands. Henry David Thoreau retreated to Walden Pond and wrote his essay on “Civil Disobedience.” James Russell Lowell mocked the soldiers as lower-class ruffians easily duped by appeals to patriotism.

Modern left-wing historians such as Paul Foos have followed Lowell’s lead, seeing an army recruited from a “despised labor force” and the war “critical in shaping the new exploitive social relations that would characterize ‘free labor’ and American capitalism in the nineteenth and twentieth centuries.” The antiwar movement has changed little over the centuries, and its vision for the country has not improved.

The Whigs won a narrow majority in the House of Representatives in the 1846 election, gaining 37 seats, but were split on the war. And those who were opposed could not decide on an alternative policy. Yet, in January 1848, with the war won, the Whigs passed an amendment in the House censuring Polk for a “war unnecessarily and unconstitutionally begun.” Soon thereafter, however, it was the war hero Zachary Taylor who won the presidency in 1848 on the Whig ticket.

Meanwhile, U.S. forces advanced from Texas into northern Mexico, and, after the sea-borne capture of Vera Cruz, marched on Mexico City. The capital fell in September 1847. Though heavily outnumbered in every major battle, the better-armed and -led Americans consistently outfought their opponents. Another U.S. column had taken Santa Fe in May, 1846.

The 1848 Treaty of Guadalupe Hidalgo met all of Polk’s territorial objectives, but did not still domestic opposition. Polk had completed America’s march across the continent, gaining strategic Californian ports to open the Pacific. Yet he was exhausted by the political struggle, and he did not seek re-election. A majority of senators in each party did come together to ratify the treaty, 38-14, showing that it is possible for bipartisanship to prevail when the national stakes are high. We can only pray that such an outcome will be the case in the future.

William Hawkins is senior fellow for national-security studies at the U.S. Business and Industry Council in Washington, D.C.


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