Today’s Republican Party has made a turn toward foreign-policy isolationism or, less pejoratively, realism and restraint. After Donald Trump shattered the GOP’s omertà about the disastrous Iraq War—a “big fat mistake,” he called it in 2016—Republicans quickly learned to decry “endless wars” and, often quite sensibly, argue for shrinking America’s global military footprint. During the 2020 election, Trump’s supporters touted his refusal to start any new wars while in office (though he got very close).

When it comes to America’s southern neighbor, however, Republicans have grown more hawkish. Party leaders, including members of Congress and presidential candidates, now regularly advocate for direct U.S. military intervention in Mexico to attack drug cartels manufacturing the deadly fentanyl flooding into America. “Building the wall is not enough,” Vivek Ramaswamy said at Wednesday night’s GOP-primary debate. The best defense is now a good offense.

The strategic stupidity of any potential U.S. military intervention in Mexico is difficult to overstate. The calls for such an intervention are also deeply ironic: Even as Trump’s epigones inveigh against the possibility of an “endless war” in Ukraine similar to those in Iraq and Afghanistan, they are reprising the arguments, tools, and rhetoric of the global War on Terror that many of them belatedly turned against.

The War on Terror was a disaster, devastating countries and leaving hundreds of thousands of people dead and millions of refugees adrift. A botched U.S. attack on Mexico, America’s largest trading partner, could create a failed state on the 2,000-mile U.S. southern border, an outcome that would be far, far worse for the United States. The toll of the U.S. fentanyl epidemic is staggering: More than 100,000 Americans died of an overdose in 2022. But a unilateral military “solution” holds the potential, if not the near certainty, of causing far more death and destruction than any drug.

[Read: ‘Every time I hear you, I feel a little bit dumber’]

Trump, not surprisingly, sowed the seeds for this new jingoism. After launching his presidential campaign in 2015 with an infamous verbal attack against Mexican migrants, in office he mused about shooting missiles at Mexican fentanyl labs, according to the memoir of his then–defense secretary, Mark Esper. “No one would know it was us,” Trump assured a stunned Esper.

Fast-forward to last month, at this election cycle’s first Republican presidential debate: Florida Governor Ron DeSantis pledged to launch Special Operations raids into Mexico on his first day in office. His rivals for the nomination have issued similar promises to wage war against the cartels—in the form of drone strikes, blockades, and military raids. Former Ambassador to the United Nations Nikki Haley breezily promised at this week’s debate to “send in our Special Operations” to Mexico. Republican senators and representatives have introduced bills to classify fentanyl as a chemical weapon, designate Mexican drug cartels as foreign terrorist organizations, and authorize the use of military force in Mexico.

If you’re inclined to dismiss this saber-rattling as primary-season bluster, don’t be so sure. Pundits and voters seem to be falling in line behind the politicians. The conservative commentator Ben Domenech recently said that he is “close to becoming a single issue voter” on the issue of attacking Mexico (he’s for it). A recent poll found that as many GOP voters consider Mexico an enemy of the United States as an ally, a marked shift from just a few years ago.

The parallels to the War on Terror aren’t exact—no prominent Republican has advocated a full-scale invasion and occupation of Mexico, at least not yet. But the rhetorical similarities are hard to ignore. America’s tragic interventions in Iraq and Afghanistan began with politicians inflating threats; seeking to militarize complex international problems; and promising clean, swift, decisive military victories. The language regarding Mexico today is eerily similar. The Fox News personality Greg Gutfeld recently assured his viewers that a unilateral attack on Mexico would “be over in minutes.” The labeling of Mexican cartel leaders as “terrorists” sidelines even the most basic analysis of the costs and consequences of a potential war. Just like in Iraq, a war on Mexico would be a war of choice, with American moral culpability for whatever furies it unleashes.

[David Frum: The new Republican litmus test is very dangerous]

It’s worth remembering that the war in Afghanistan included a failed counter-drug campaign. In my time there as a Marine lieutenant a decade ago, U.S. troops engaged in erratic, futile attempts to interrupt opium-poppy cultivation. Partnered with Afghanistan’s version of the U.S. Drug Enforcement Agency, my company wasted days fruitlessly searching motorcycles at checkpoints on dusty village trails, finding no drugs. On one occasion, I was ordered to confiscate farmers’ wooden poppy scorers, simple finger-mounted tools used to harvest opium; at a cost of maybe a penny a piece, they were immediately replaced. U.S. planes bombed 200 Afghan drug labs during the occupation. Yet opium production skyrocketed—Afghanistan produced more than 80 percent of the global supply of the drug in the last years of the war.

Mexico would be an even riskier proposition. Start with the obvious: proximity. The direct costs to the United States of the War on Terror were enormous: $8 trillion squandered, more than 7,000 U.S. troops killed in action, tens of thousands wounded. Across the Middle East, North Africa, and Central Asia, hundreds of thousands of people, most of them civilians, were killed in counterinsurgency campaigns and civil wars. Governments were toppled, leaving behind anarchy and nearly 40 million refugees, who have further destabilized the region and its neighbors. But America itself was shielded from the worst effects of its hubris and militarism. Flanked by oceans and friendly neighbors, Americans didn’t have to worry about the conflicts coming home.

Any unilateral U.S. military action in Mexico would risk the collapse of a neighboring country of 130 million people. It could unleash civil war and a humanitarian crisis that would dwarf those in Iraq and Syria. This carnage would not be confined to Mexico. Some of America’s largest and wealthiest cities are a few hours’ drive from the border; nearly 40 million Americans are of Mexican descent, many of them with family members still living across the border. The cartels would not have far to travel to launch retaliatory terrorist attacks on U.S. soil. And the refugee crisis that many Republicans consider the preeminent national-security crisis would worsen.

The United States would also lack one major War on Terror asset: partners. A host of NATO and non-NATO partners contributed troops and resources to the fighting in Afghanistan; none would be willing to participate in an American attack on Mexico. Despite government corruption in Iraq and Afghanistan and dependency on U.S. weapons and technology, soldiers from those countries did the lion’s share of the fighting and dying in the long struggle against insurgents there. But Mexican President Andrés Manuel López Obrador has publicly rejected U.S. military intervention. One can easily imagine uniformed Mexican soldiers and policemen firing on American troops and aiding the cartels. If the U.S. were to attempt to build competing Mexican militias or proxies in response, it would further fracture the Mexican state.

[David Frum: The autocrat next door]

If there is an overriding lesson of America’s post-9/11 conflicts, it is that war unleashes a host of unintended consequences. A war of choice seldom respects the goals or limits set by its architects. External military intervention in a country fighting an insurgency—ideological, criminal, or otherwise—is particularly fraught. Foreign troops are far more likely to be an accelerant of violence than a dampener. As in Iraq and Afghanistan, cartel members would be likely to hide out among civilians, infiltrate Mexico’s already compromised security services, and find havens in bordering countries (the United States included). American forces would in turn be susceptible to corruption and infiltration, especially if an intervention were to drag on longer than expected.

Lacking a definable end state, a counter-cartel campaign would likely devolve into a manhunt for a few narco kingpins. Such an operation would be liable to create folk heroes out of brutal drug traffickers, one accidental wedding-party drone strike at a time. Some of the worst men on Earth could become global symbols of resistance to U.S. imperialism, especially if they are able to evade U.S. forces for a decade, as Osama bin Laden did. A U.S.-Mexico conflict would then become an opportunity for other American adversaries. Russia and China would undoubtedly be happy to arm the cartel insurgents, perhaps even overtly. Mexico already hosts more members of the GRU—Russia’s military intelligence—than any other foreign country. American arms and assistance are taking Russian lives in Ukraine, as they did in Afghanistan a generation before. The Russians would welcome an easy opportunity to return the favor.

Since Trump’s ascent in 2016, the most bellicose neoconservatives in the GOP have been ousted, the Republican Party’s views on Russia and China have become muddled, and the Iraq War is now widely accepted as a disaster. But Republicans’ enthusiasm for launching a war on Mexico reveals the shallowness of their conversion. The rise of fentanyl is mostly a demand-side problem. Whatever Republican leaders say about “endless wars,” they’re once again pulling out the military hammer first, then looking for nails.

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