As part of its “America 250” campaign, the Trump White House on Tuesday issued a presidential pronouncement commemorating what it calls “our victory in the Mexican-American War.”

The statement portrays the 1846–48 conflict as a defensive war forced upon an innocent United States by Mexico, culminating in a “legendary” conquest that fulfilled the sacred mission of “Manifest Destiny” that was “beating in every American heart” to dominate the continent.

It celebrates the capture of Mexico City and the seizure of more than half of the neighboring country’s territory, in Orwellian fashion, as a triumph of “American sovereignty.” And it draws a straight line from the “fields of Mexico” to today’s militarized border and a rearmed, blood-drenched Monroe Doctrine for the 21st century. In this way, the Trump administration enlists the crimes of the 19th century in preparation for the crimes of the 21st.

Absent in the White House statement is any real accounting of why the war was launched, whose interests it served, and what followed from it. Above all, the statement ignores the experience’s most elementary lesson: that the predatory war against Mexico, waged to build “an empire for slavery,” led directly to the Civil War, a great social revolution that destroyed the very slave system the Mexican-American War had been fought to perpetuate.

It is a historical maxim that the plotters of aggressive wars do not fathom the revolutionary consequences of their actions. So it was with President James K. Polk (1845-1849) and the slave-holding elite in the 1840s who organized the seizure from Mexico of more than half its territory. And so it is today, as Trump’s drive to extend US power ever more aggressively across the hemisphere and the entire planet unleashes social and political explosions that will not unfold according to the designs of the conspirators now falsifying the past to justify new wars of conquest.

The White House pronouncement’s aggressiveness is matched only by its ignorance. The familiar warning that those who fail to learn from history are doomed to repeat it applies here with unusual force. Trump is, by every measure, the most historically illiterate president in American history—past statements have shown he does not even understand its basic chronology—and there is no reason to suppose that the circle of fascist ideologues and bootlicking sycophants surrounding him is any better informed. The America 250 statement bears all the marks of this gaping intellectual vacuum.

The origins of the Mexican-American War are complex, involving the political histories of two countries, but the basic logic can be stated simply. This is to be found not in Mexican aggression against the United States, as Trump claims, but in the expansion of American slavery into Mexico.

Well before the 1840s, Anglo-American slaveholders had poured into Texas, then called Tejas, seeking to spread the cotton economy into Mexico, which had abolished slavery in 1829. In 1836, the Anglo slave-holding elite declared independence and fought off efforts to recapture Texas by the central government of Antonio López de Santa Anna, which had been weakened by bitter internal dissent and rebellion in other regions as far away as the Yucatan. The settlers’ victory set up the short-lived Republic of Texas.

Few contemporaries were in doubt about the trajectory of these events. Texas was bound for American annexation. This was completed in the first year of the Polk administration. The annexation, in effect, ratified and protected the slaveholders’ rebellion against Mexican authority. But having annexed Texas, a war against Mexico then became the only means by which that conquest could be secured and extended westward.

It was with this goal in mind that Polk ordered US troops under General Zachary Taylor into the disputed strip between the Nueces River and the Rio Grande—territory Mexico still claimed—precisely to provoke a confrontation. When the inevitable clash took place, which Trump’s statement characterizes as an “ambush,” Polk seized on it to demand war.

Polk’s assertion that “American blood” had been shed on “American soil”—a claim that Trump recycles as good coin—has long been viewed by historians as among the most cynical casus belli in American history. This takes on its full meaning only when considered alongside its rivals for the dubious distinction: McKinley’s promotion of the sinking of the USS Maine to justify war with Spain in 1898 and the seizure from it of Puerto Rico, Cuba and the Philippines; Wilson’s use of the Zimmerman Telegram to enter World War I against Germany in 1917; and Lyndon Johnson’s exploitation of the bogus “Gulf of Tonkin incident” to vastly expand the American presence in Vietnam in 1964. More recent years have seen the “weapons of mass destruction” claims against Iraq and the allegations of “narco-terrorism” against Venezuela. In each case, a manufactured or exaggerated pretext functioned as the tripwire for wars whose economic, political and strategic aims were already in place and would have been pursued regardless.

In the case of the Mexican-American War, Polk’s actions were the product of the determination of Southern planters and speculators to acquire new territory, it being widely understood that the slave system depended on expansion for its survival. Moreover, the leaders of the Democratic Party, which dominated American politics at the time, believed that territorial expansion would submerge the explosive slavery question beneath a wave of national patriotism.

The Democratic-aligned media had even developed an ideology that shrouded this expansionism in a quasi-religious and racial cloth: Manifest Destiny, coined by journalist John O’Sullivan in 1845, which presented expansion at the expense of the Indians, Mexicans and Canadians as ordained by providence.

The war against Mexico at first appeared to fulfill these promises. US forces routed Mexico’s unprepared army, occupying Mexico City in September 1847—an event that Trump’s proclamation celebrates. But even when viewed through the lens of military history, the triumph suggests its own star-crossed fate. The very officers who served together against Mexico would, little more than a decade later, lead the Confederate and Union armies against each other in the Civil War, among them Robert E. Lee, Thomas J. “Stonewall” Jackson and James Longstreet, for the secessionists; Ulysses S. Grant, William Tecumseh Sherman and Winfield Scott Hancock for the Union.

Grant later recalled in his important autobiography brought out with the help of Mark Twain,

For myself, I was bitterly opposed to the measure, and to this day regard the war which resulted as one of the most unjust ever waged by a stronger against a weaker nation. It was an instance of a republic following the bad example of European monarchies, in not considering justice in their desire to acquire additional territory.

Later in the memoirs he also connects the Mexican War directly to the coming of the Civil War, writing:

The Southern rebellion was largely the outgrowth of the Mexican war. Nations, like individuals, are punished for their transgressions. We got our punishment in the most sanguinary and expensive war of modern times.

Even in its own time, the patriotic enthusiasm over the Mexican war, that “wicked war,” as Grant called it, was short-lived. Indeed, before it began, Polk’s ambitions managed to deepen the fissures that were widening in American society. Former president John Quincy Adams, the tireless opponent of the ban on reading anti-slavery petitions in the US Congress known as the “gag rule,” and the lawyer who defended the enslaved Africans who mutinied aboard the Amistad in 1840, led the fight against the Polk administration. Adams collapsed from a massive stroke on the floor of Congress on February 21, 1848, his last word “No,” a vote against a commendation of the generals who led the victory over Mexico.

Abraham Lincoln, who overlapped for one term with Adams and served as a pallbearer at his funeral, also vociferously opposed the war, most famously in his “Spot Resolutions,” which demanded that the Polk administration show “the soil was ours” on the spot where the alleged Mexican attack on American forces had taken place. Polk was guilty, Lincoln said, in uncharacteristically harsh terms, of “the sheerest deception. … He feels the blood of this war, like the blood of Abel, is crying to Heaven against him.” Later, in another speech, Lincoln warned of nationalism as a narcotic used to mask a war of conquest, which he described as “military glory—that attractive rainbow that rises in showers of blood.”

Henry David Thoreau refused to pay taxes in protest, went to jail, and concluded that “if the alternative is to keep all just men in prison, or give up war and slavery, the State will not hesitate which to choose.” Frederick Douglass, in typically direct fashion, condemned the conflict as “a war for the extension of slavery,” waged, he insisted, “not for freedom, but for slavery, not for justice, but for oppression.” Ralph Waldo Emerson offered a warning: “The United States will conquer Mexico, but it will be as the man who swallows arsenic, which brings him down in turn. Mexico will poison us.”

Emerson’s prophecy was realized even more quickly than he might have expected. Gold was discovered in California just days before the Treaty of Guadalupe Hidalgo was signed, drawing tens of thousands of prospectors, tradesmen and entrepreneurs committed to “free labor.” California entered the Union as a free state in 1850, shattering Southern dreams of a slave empire stretching to the Pacific.

Shocked at the loss of California—and the attack by northern “barnburner” Democrats led by David Wilmot of Pennsylvania, who had attempted, unsuccessfully, to block slavery from all territories taken from Mexico—the Southern elite demanded redress. They obtained it in the infamous Compromise of 1850, which paired California’s admission with an extraordinarily harsh Fugitive Slave Act, among other measures.

The “compromise” poured fuel on an already spreading fire. The Fugitive Slave Act nationalized the slave catchers’ trade, compelling Northern officials and citizens to assist in the seizure of alleged fugitives and provoking mass resistance among the people of cities in towns in Massachusetts, Wisconsin, Pennsylvania and other states. Vigilance committees spread across Northern cities, organizing networks to shelter fugitives, obstruct renditions and openly defy federal authority.

In both its methods and its aims, the Fugitive Slave Act bears striking resemblance to Trump’s ICE dragnet raids, mass deportations and concentration camps for immigrants—both are mobilizations of federal authority to hunt down a targeted population and eviscerate basic democratic rights. And just as the slave catchers’ regime generated an upsurge of organized defiance in the 1850s that led to the Civil War, so today there is massive and growing resistance among workers and youth to the criminalization and persecution of immigrants.

It is precisely here that the immigrant question opens back onto the larger history of the Mexican-American War itself. The people whom Trump vilifies as alien “invaders” are, to a significant extent, the descendants of those peoples whose lands and communities were split in two by the new boundary lines drawn in 1848.

The Treaty of Guadalupe Hidalgo formalized the seizure of an immense expanse of territory, transferring to the US what would become California, Nevada, Utah, most of Arizona and New Mexico, and parts of Colorado and Wyoming, while confirming the earlier annexation of Texas. No previous American war had yielded territorial gains on this scale.

But the new border attempted to divide what could not, in the long run, be made separate: an integrated regional economy and a population bound together by ties of labor, community and commerce. In 1848, tens of thousands of Mexican citizens and Native Americans were abruptly transformed into conquered minorities within the US. Over time, far larger numbers crossed the same border line—not as invaders, as claimed by Trump, who has never worked a day in his life, but as workers drawn north by the relentless demands of American capitalism.

Today, the principal prizes of the 1840s conquest—California and Texas—are economic giants with large, diverse working populations deeply interconnected to Latin America and Asia. Mexican and Central American workers live and labor alongside US-born workers not only in these states, where they and their descendants make up about 40 percent of the population, but across the country, from the Rio Grande to Minnesota’s packinghouses and fields. The attempt to target them is a desperate effort to deny history and objective reality, and to reimpose national and racial divisions on a working class forged through nearly two centuries of economic integration.

Trump’s invocation of the Mexican-American War does not merely falsify history. It revives a political tradition that seeks to smother social contradictions with nationalism and war. History records the outcome of that experiment: the war against Mexico did not stabilize American society—it helped tear it apart. The same resort to chauvinism and external aggression today will likewise accelerate, not avert, the reckoning that is coming.