Ivo Daalder, former U.S. ambassador to NATO, is a senior fellow at Harvard University’s Belfer Center and host of the weekly podcast “World Review with Ivo Daalder.” He writes POLITICO’s From Across the Pond column.

U.S. President Donald Trump loves the 19th century.

His heroes are former presidents William McKinley who “made our country very rich through tariffs,” Teddy Roosevelt who “did many great things” like the Panama Canal, and James Monroe who established the policy rejecting “the interference of foreign nations in this hemisphere and in our own affairs.”

These aren’t just some throw-away lines from Trump’s speeches. They signify a much deeper and broader break from established modern national security thinking.

Trump is now the first U.S. president since Franklin D. Roosevelt to believe the principal threats to the U.S. aren’t in far-away regions or stem from far-away powers — rather, they’re right here at home. For him, the biggest threats to America today are the immigrants flooding across the country’s borders and the drugs killing tens of thousands from overdoses.

And to that end, his real goal is to dominate the entire Western hemisphere — from the North Pole to the South Pole — using America’s superior military and economic power to defeat all “enemies,” both foreign and domestic.

Of course, at the top of Trump’s list of threats to the U.S. is immigration. He campaigned incessantly on the idea that his predecessors had failed to seal the southern border, and promised to deport every immigrant without legal status — some 11 million in all — from the U.S.

Those efforts started on the first day, with the Trump administration deploying troops to the southern border to interdict anyone seeking to cross illegally. It also instituted a dragnet to sweep people off the streets — whether in churches, near schools, on farmlands, inside factories, at court houses or in hospitals. Even U.S. citizens have been caught up in this massive deportation effort. No one is safe.

The resulting shift is also expectedly dramatic: Refugee admissions have halted, with those promised passage stuck in third countries. In the coming year, the only allotment for refugees will be white South Africans, who Trump has depicted as genocide victims. Illegal crossings are down to a trickle, while large numbers of immigrants — legal as well as illegal — are returning home.

And 2025 will likely be the first time in nearly a century where net migration into the U.S. will be negative.

For Trump, immigrants aren’t the only threat to the homeland, though. Drugs are too.

That’s why on Feb. 1, the U.S. leader imposed tariffs on Canada, Mexico and China because of fentanyl shipments — though Canada is hardly a significant source of the deadly narcotic. Still, all these tariffs remain in place.

Then, in August, he called in the military, signing a directive that authorizes it to take on drug cartels, which he designated as foreign terrorist organizations. “Latin America’s got a lot of cartels and they’ve got a lot of drugs flowing,” he later explained. “So, you know, we want to protect our country. We have to protect our country.”

And that was just the beginning. Over the past two months, the Pentagon has deployed a massive array of naval and air power, and some 10,000 troops for drug interdiction. Over the past five weeks, the U.S. military has also been directed to attack small vessels crossing the Caribbean and the Pacific that were suspected to be running drugs. To date, 16 vessels have been attacked, killing over 60 people.

When asked for the legal justification of targeting vessels in international waters that posed no imminent threat to the U.S., Trump dismissed the need: “I think we’re just going to kill people that are bringing drugs into our country. Okay? We’re going to kill them. You know, they’re going to be, like, dead.”

But now the U.S. leader has set his sights on bigger fish.

Late last month, the Pentagon ordered a carrier battle group, Gerald R. Ford, into the Caribbean. Once that carrier and its accompanying ships arrive at their destination later this week, the U.S. will have deployed one-seventh of its Navy — the largest such deployment in the region since the Cuban Missile Crisis in 1962.

If the target is just drug-runners in open waters, clearly this is overkill — but they aren’t. The real reason for deploying such overwhelming firepower is for Trump to intimidate the leaders and regimes he doesn’t like, if not actually force them from office. Drugs are just the excuse to enable such action.

The most obvious target is Venezuela’s Nicolás Maduro, who blatantly stole an election to retain power last year. The White House has declared Maduro “an illegitimate leader heading an illegitimate regime,” and Trump has made clear that “there will be land action in Venezuela soon.”

However, Maduro isn’t the only one Trump has his eye on. After Colombian President Gustavo Petro accused the U.S. of killing innocent fishermen, Trump cut off all aid to the country and accused Petro of being “an illegal drug leader,” which potentially sets the stage for the U.S. to go after another regime.

All this firepower and rhetoric is meant to underscore one point: To Trump, the entire Western hemisphere is America’s.

Leaders he doesn’t like, he will remove from power. Countries that take action he doesn’t approve of — whether jailing those convicted of trying to overthrow a government like in Brazil, or running ads against his tariffs as in Canada — will be punished economically. Greenland will be part of the U.S., as will the Panama Canal, and Canada will become the 51st state.

Overall, Trump’s focus on dominating the Western hemisphere represents a profound shift from nearly a century’s-long focus on warding off overseas threats to protect Americans at home. And like it or not, for Trump, security in the second quarter of the 21st century lies in concepts and ideas first developed in the last quarter of the 19th century.