In February, former U.S. President Donald Trump encouraged Russia’s leadership to do “whatever the hell they want” to any NATO member that does not spend two percent of its GDP on defense. Trump has made similar incendiary comments before. Europe should take his threats seriously. He is once again the presumptive Republican candidate for president of the United States, and he leads Joe Biden, the incumbent, in many recent polls.

Should he be elected to a second term, Trump’s attitudes toward Ukraine, Russia, and NATO—and his mercurial and self-interested mindset—will be pivotal for the war in Ukraine. Trump will likely disrupt the entire transatlantic relationship far more than he did during his first presidency. Although European leaders met his election in 2016 with panic, the policies he pursued were more or less conventional. He did not withdraw from NATO, and his administration delivered lethal military aid to Ukraine that proved crucial to the country’s self-defense after Russia’s invasion. Between 2017 and 2021, not much got permanently broken in the transatlantic relationship.

The risks of a second Trump term would be more dangerous. They would reside in the diminishment of the United States as a credible security guarantor for Europe. Even if Trump maintains U.S. military support for Ukraine, which is improbable, his highly transactional foreign policy would embolden Russian President Vladimir Putin and hamper Ukraine’s war effort. Europe would not have enough time to unite and arm itself to resist an expansionist Russia. With Trump as president, Putin could very soon get what he wants: control over large swaths of Ukrainian territory. Such a development would have knock-on effects throughout the continent, leaving Europeans with less and less control over their own geopolitical destiny.

Fears about a second Trump term often crystallize around the discrete decisions he might take. He could decide to pull out of NATO. He could decide to throw Ukraine under the bus. He could decide to pursue the partnership with Putin he has so often talked about with fondness. The reality, though, is that Trump is not decisive. He rarely follows through on his most reckless ideas. But it is Trump’s mercurial nature, more than his ideals, that could wreak havoc. He would undoubtedly stack his cabinet, and even the United States’ military leadership, with loyalists.

And the world is more flammable now than it was in 2016. War at Europe’s doorstep, war in the Middle East, and the possibility of a major conflict in Asia would be the backdrop to a second Trump presidency. A fickle man, Trump gets his head turned by other leaders, including Putin, North Korea’s Kim Jong Un, and China’s Xi Jinping. He has transformed the Republican Party in his image, something that was not the case in 2016. Among Republicans, there are fewer and fewer Atlanticists left. Within the party, the idea that the United States should not be responsible for Europe’s security has become mainstream. The threats that emerge from Trump’s behavior will haunt Europe even if Trump does not win in November.

NEAR MISS

After Trump’s 2016 election, many foreign leaders hedged their bets, anticipating a shift in U.S. foreign policy but also operating in a wait-and-see mode. The possibility that Trump’s attitudes would prove an exception to the traditional spirit of U.S. policy was very real. True, Trump had been elected. Yet he had lost the popular vote. Such hedging was wise. In the 2018 midterm election, the Democratic Party made inroads, and throughout his presidency, Trump’s administration found ways to defy the president’s less palatable directives.

The so-called adults in the room—officials such as Secretary of Defense Jim Mattis, National Security Adviser H. R. McMaster, and Secretary of State Rex Tillerson—blunted Trump’s most disruptive impulses. Although Trump’s rhetoric was often anti-NATO—he declared the alliance “obsolete” in January 2017—NATO did not wither during his first term; it grew. Trump allowed two new countries, Montenegro and North Macedonia, into the alliance. Together with Russia’s belligerent behavior, Trump’s continual questioning of the United States’ commitment to Europe stimulated European countries to make small increases in their defense spending.

Russia cast a shadow over the first Trump presidency. The Kremlin meddled in the 2016 election, attempting to tip the scales in Trump’s favor. Scandals, court cases, and an independent prosecutor’s probe kept Trump’s relationship with Russia in the headlines. Parts of this media spectacle were cultivated by Trump, who loves playing the victim, and other aspects were fanned by the suspicion, endlessly discussed during his presidency, that Trump was a Russian agent. Indeed, Trump was friendlier to Putin than anyone in the top ranks of U.S. politics had ever been. But no transformative shift in the United States’ relations with Russia ever came to pass—no deal to accept Russia’s annexation of Crimea, no deal to end the war in eastern Ukraine on Russia’s terms, no deal to expand Russia’s influence over Europe. Trump did not lift the Russia-related sanctions previous presidential administrations had imposed. During his presidency, Republican legislators voted to expand them.

Among the most consequential acts of Trump’s presidency was the lethal military assistance he provided to Ukraine. His motives were far from pure. Aiding Ukraine with lethal weapons was something President Barack Obama had refused to do, and Trump was never happier than when he could overturn an Obama-era policy. In 2017, Trump greenlighted lethal military aid including Javelin antitank missiles to Ukraine, an act he believed would be good for the U.S. defense industry. In 2019, he held up deliveries while his envoys prodded the Ukrainian government to smear Biden’s reputation. But ultimately, the aid continued to arrive. In the first few weeks after Russia’s 2022 invasion, those Javelin antitank systems would play a crucial role in Ukraine’s ability to defend itself against Russia’s advance toward Kyiv.

TRANSACTION COSTS

These precedents, however, should provide little reassurance. A second Trump term would almost certainly be more radical. Trump and his acolytes better know how to rule the executive branch. His team has been preparing an overhaul of the federal government designed to install Trump loyalists in posts mostly occupied, during his first term, by nonpartisan civil servants and appointees who had no strong ideological affinity for Trumpism. Republican primary voters and party officials have rallied behind Trump as their 2024 nominee, meaning that Trump’s whims and Trump’s ideas, which can change from day to day, would be more likely to be executed were he to regain power.

A second Trump term would show that the principles underlying U.S. foreign policy have truly changed. With Trump crowned the presumptive 2024 Republican presidential nominee, this shift in perception has already begun. His reelection would be a sea change in domestic and foreign policy—a lasting turn away from alliance-building and the belief that the United States is Europe’s natural ally and security guarantor. Trump would likely pursue a kaleidoscopic array of short-term partnerships, most of them with countries outside of Europe and some with countries hostile to Europe. He treats Atlanticism as Democrats’ foolish preoccupation, and this could no longer be understood as some temporary anomaly. Instead, the chapter that began in 1945 would draw to a close. It would become history. Russia would surely conclude that Atlanticism is a moribund viewpoint.

Transactionalism was the one coherent thread that ran through Trump’s first term. A second Trump term would likely orient itself around a less restrained transactionalism, leaving American foreign policy subordinate to Trump’s self-interest and to his attempts to dominate the fast-moving U.S. news cycles. A defining feature of Trump’s first presidency was the absence of large-scale wars in Europe or Asia. For four years, Trump’s inflammatory rhetoric found little kindling. But this global outlook has changed. By January 2025, the best outcome that could plausibly be achieved in the Israel-Hamas war would be a nervous cease-fire. It is not inconceivable that crises related to North Korea or Taiwan will break out before then.

And most important, the war in Ukraine will almost certainly not be over. Russia’s invasion of Ukraine spurred Europeans to invest more in their own defense. By next year, 18 NATO member states will finally reach a defense spending at two percent of GDP. In Trump’s eyes, these investments are destined to fall short.

His complaints that European allies “lag” behind the United States in their military spending have never been sincere. In truth, he sees little value in the United States’ participation in NATO at all. His broadsides against the alliance are not only about policy disagreements—they are also populist theater for domestic consumption. If such theater seemed essentially harmless in his first term, it would be much more dangerous over the next four years. Mere approving nods toward Russia’s destabilizing ambitions beyond Ukraine could be disastrous for Europe. Back in 2016, Russia was an unwanted military presence in Ukraine, but the contours of its global ambitions were only dimly visible. Now, an internationally hyperactive Russia wants to remake Europe’s entire security architecture through war.

RUSSIAN ROULETTE

Writing in Foreign Affairs in February, a set of European leaders and analysts argued that a second Trump administration could jump-start Europe’s transition to full strategic autonomy. European countries have the option of issuing joint debt to surge the continent’s defense production, as they did during the COVID-19 pandemic. But such efforts, even if all the necessary parties agreed to them, would take time. Europe would need at least a decade to gear up to defend itself successfully against a Russia that is continually increasing its defense budget.

Trump could also compel individual European countries to go their own way instead of joining forces, provoking a divisive “seek shelter” moment. Realizing that the United States is pulling away from Europe, each European country might react to the Russian threat differently. A second Trump term could fracture instead of harden Europe—just the outcome that Russia would like to see.

Trump cannot destroy the EU, but he can dramatically undermine NATO. He need not withdraw from the alliance, which would be procedurally messy. He could fill top positions with loyalists who hold Atlanticism in contempt, eroding the trust of the United States’ European allies. (One such figure is Richard Grenell, his former ambassador to Germany, who may become Secretary of State.) As president, Trump would have the power to draw down the quantity of U.S. troops stationed in Europe and to threaten that Washington might not honor its Article 5 commitments. The delight Trump takes in undoing his predecessors’ achievements is telling: he relished withdrawing from Obama’s Iran deal and from the 2015 Paris climate accords. In 2025, Trump could try to undo the very methods that the Biden administration has employed to reassure Europe after Russia invaded Ukraine—such as stationing additional troops in Europe and helping to backfill for European countries that were giving their military equipment to Ukraine.

A second Trump term would make it far easier for Russia to undermine NATO from within.

Russia’s invasion of Ukraine did not bother Trump. At times, he refers to it as proof of American weakness—Biden’s fault. At other times, he speaks in praise of Putin’s aggression. Rather than immediately pulling U.S. military and intelligence aid from Ukraine, Trump might try to bargain with Putin if he thinks that Russia could offer him something in return, materially or politically: a “peace in our time” for which he could take credit or a more mundane proposition such as lower oil prices. Trump could then claim to be standing up for the American people. He could contend, accurately or inaccurately, that money once earmarked for Ukraine will be spent on securing the U.S. southern border. Trump could also seek to use U.S. aid for Ukraine as leverage over Europe, to be given or taken away in proportion to what Europe can give to the United States.

Overall, a Ukraine at war does not have anything tangible to offer either to Trump’s businesses or to his political position. Trump does not believe that Ukraine is helping the United States by defending itself, shoring up European security, or boosting U.S. arms manufacturing. He makes no arguments about the intrinsic value of Ukraine’s sovereignty, territorial integrity, and European security. To him, these principles are just fodder for negotiation.

If Ukraine’s future were to become Trump’s bargaining chip, that could prompt a series of shattering knock-on effects. If Russia consolidates its hold on Ukraine, an incursion into Moldova would be a natural choice. Trump cares as much about Moldova as he does about Ukraine—very little. The threat to Europe’s eastern states would increase exponentially. And were Trump to pull the rug out from under NATO, Putin might develop expansionist ambitions even beyond Moldova and Ukraine. He could test NATO’s resolve by launching unattributed incursions—by troops without insignia, for example—into the Baltic states or Poland, not to hold NATO territory but to instill fear in NATO members by demonstrating that the alliance is hollow.

Without strong U.S. backing for NATO, such moves by the Kremlin would pose a terrible dilemma for France, Germany, the United Kingdom, and other NATO allies. Out of fear, some European states might be tempted to appease Russia instead of responding to such incursions with military force. Countries such as Hungary might even side with Russia while remaining in NATO, passing intelligence to Moscow, mocking the idea of a unified alliance, and gumming up European decisions that rely on consensus. Thus, Russia could undermine NATO from within.

EFFECTS OF CHARACTER

More likely than a direct Russian assault on NATO would be a Trump-brokered deal that gives Putin control over large parts of Ukraine and, via a withdrawal of U.S. troops stationed in Europe, a nontrivial say in European security. With such a deal, Putin would be seeking a permanent stake in European security, rolling back NATO to its 1997 configuration, for example, as he demanded in December 2021. To increase pressure on Europe, Russia could even threaten nuclear strikes against Europe. He has done so before. This time, his threats would hold more weight, because Europe could no longer depend on the U.S. nuclear umbrella. Trump could then blackmail Europeans with the leverage he has acquired over their security, demanding that U.S. protection be paid for with concessions on trade or on Europe’s approach toward China.

Trump lacks the patience to follow through on most of his diplomatic agendas. His tendency is to submerge his actual intentions in a flood of contradictory statements. He is unlikely to impose a new European security architecture or a settlement to the war in Ukraine of his own making. He does not have the vision.

Yet his plans will matter less than his character. Profoundly amoral, Trump will do anything he thinks will get him attention, make him money, or enhance his power and position. Because he will be more unbound in a second term, because European countries’ efforts to strengthen themselves have been insufficient, and because Putin’s boldness is growing, in the blink of an eye Trump could wreck the transatlantic relationship. Were he able to sell the destruction of the United States’ historic ties with Europe as a win, he would do so, leaving Ukrainians and Europeans in the lurch, suddenly vulnerable to Russia’s unchecked ambitions. Europe would find itself trapped between the Scylla of an aggressive Russia and the Charybdis of an ambivalent United States, unsure whether it prefers to ignore or exploit Europe. It is no fantasy that, instead of perpetual peace—and instead, even of an iron curtain—chaos could again descend on a continent all too familiar with war.

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