“Wouldn’t it be a wonderful thing,” then-presidential candidate Donald Trump mused in August, “if we actually got along with Russia and worked out some kind of deal where we go and knock the hell out of ISIS along with NATO and along with the countries that are in that area?” At other times, however, Trump publicly imagined himself engaged in a very different NATO initiative. Under this scenario, he would denounce America’s European allies as freeloaders and force them to accept a deal requiring them to pay a much bigger share of the alliance’s defense burden.

On first glance, these two initiatives don’t seem mutually exclusive, and Trump will be tempted to pursue both of them once he becomes president. But he’ll soon discover that he can’t have it both ways, and it is all too likely that his partnership with Russian President Vladimir Putin will lead to the dramatic weakening of NATO.

To see the risks involved, suppose that Trump follows through on his idea of joining Putin in an all-out war in support of Bashar al-Assad’s dictatorship in Syria—as he put it, “Syria is fighting ISIS, and you have to get rid of ISIS.”

As they announce their alliance in the Mideast, the two strongmen solemnly declare that they will also extend their détente to Eastern Europe, where military tensions have recently been escalating. Since Russia’s invasion of Ukraine, its air and naval forces have been engaging in a series of hostile incursions along the European frontier. In response, NATO has launched its own build-up—to the point where it will be placing St. Petersburg within firing distance of short-range missiles (that could carry nuclear warheads). Given their Mideastern partnership, it would only make sense for Putin and Trump to call a halt to this dangerous escalation, and announce their intention to engage in future confidence-building measures.

But as their war against Assad’s enemies drags on for months and years, suppose that Putin reconsiders this larger détente. He begins preliminary planning for a Ukrainian-style takeover of the Baltic states. Under this scenario, local Russian minorities in Estonia or Latvia engage in “spontaneous” uprisings backed by poorly disguised Russian ground troops streaming across their borders. In weighing this aggressive strategic shift, Putin recognizes that the Baltic countries, unlike Ukraine, are members of NATO, and thereby entitled to protection under Article 5 of the alliance’s treaty. Nevertheless, perhaps Trump and others might be willing to blink and accept Putin’s loud assertions that his troops had nothing to do with the seizure of power by natives sympathetic to the Russian cause?  

Here is where Trump’s parallel effort to force Europe to stop the NATO “free-loading” becomes important. When highlighting the problem in his 2017 State of the Union, America’s new president could make a very strong case for his initiative. He could emphasize that the Europeans themselves have pledged that each NATO country would devote 2 percent of its GDP to military expenditure—and yet all major Continental powers have failed to fulfill their commitments. Germany, for example, has only invested 1.2 percent of GDP in defense. Nevertheless, given Europe’s massive fiscal crisis, the Continental powers will predictably try to deflect Trump’s demand for big increases—generating a series of bitter confrontations that will put grave stress on traditional trans-Atlantic understandings.

As Putin observes the trans-Atlantic name-calling, he will be sorely tempted to take his chances on a rerun of a Ukrainian-style takeover. As the Russians encourage their initial round of “spontaneous” uprisings, Trump will suddenly confront his moment of truth: Will he abandon his Middle Eastern alliance with Putin, and support decisive NATO action to repel the looming Russian threat? Or will he be so disgusted by the squabbling Europeans that he will permit the slow-motion incorporation of chunks of the Baltic states into the Russian Federation—and destroy the credibility of NATO’s guarantee of mutual defense?

Long-distance psychoanalysis isn’t my specialty, but I could readily imagine Trump telling the “selfish” Europeans to go to hell—employing a rhetorical variation on his response to the prospect of war between North Korea and America’s long-time ally, Japan: “Good luck. Enjoy yourself, folks.” As NATO disintegrates, the Russians will reestablish an expanding sphere of influence in Eastern Europe. In the meantime, Western Europeans will desperately remilitarize to defend themselves, since they can no longer count on the United States to help counter future threats.

This nightmare scenario suggests that Trump cannot responsibly delay a choice between Putin and NATO. If he chooses NATO, the president-elect, once in office, should refuse to join Russia in all-out support for the Assad dictatorship. It is far better for him to make an independent break with Obama’s failed strategies in the Middle East. This will allow Trump to make a burden-shifting agreement with NATO one of his primary objectives.

Suppose that Trump puts NATO first. Is there any reason to think that the Europeans, beset by so many other problems, will go along with a substantial hike in their defense contributions?

German Chancellor Angela Merkel will play a central role here. As the Continent’s economic powerhouse, Germany will have to accept a big share of the increased burden. At the same time, it has a powerful national interest in keeping the Eastern frontier as far east as possible. If NATO disintegrates, Germany will be forced to increase its military investments dramatically in response to Putin’s advances in Eastern Europe. The trillions it will then spend would far exceed the sums that Trump will be demanding.

In contrast, a successful agreement with Trump will sharply reduce the chances of Russian aggression. Consider that Putin presides over a declining and aging population of about 140 million, whose prosperity is heavily dependent on oil prices. His military only looks formidable if Trump moves in the direction of détente with Russia. Once Trump has reaffirmed America’s commitment to the alliance, only a foolish adventurer would attempt a Baltic takeover—and Putin is no fool.  

Nevertheless, Merkel will have a tough time gaining political support for a reasonable deal with Trump. While she has recently backed plans for increased military investment, she will have trouble sustaining political momentum for this initiative. She faces a serious electoral test next year, with the extreme Right gaining substantial parliamentary representation for the first time in modern German history. She is likely to emerge from the elections at the head of a broad coalition which includes leftist parties with strong pacifist leanings. They are likely to urge her to reject any big hike in expenditure, on the grounds that it will propel the country down the path of militarization that led to such catastrophe in the 20th century. Similar dynamics will confront other European leaders. Will they rise to the occasion and try to convince their fellow citizens that a reinvigorated trans-Atlantic alliance is worth the price demanded by the self-promoting deal-maker from Washington?

We won’t find out unless President Trump makes a New Deal on NATO a high priority—and successfully trades a renewed American commitment to defend the Eastern European frontier for a new European commitment to bear a fair share of the costs. He is deluding himself if he thinks he can have it both ways, and also try to make America Great Again with the aid of Vladimir Putin.