This reasoning was abandoned by post-Cold War presidents, and especially by George W. Bush, in the heady days when it appeared that America could project power as easily in Kabul as in the Caribbean. And despite the Iraq disaster most of Bush’s would-be Republican heirs — John McCain and Mitt Romney as well as Rubio and Jeb! — maintained a similarly maximalist posture, in which every theater was supposedly a vital one, every tyrant a potential enemy, and we should be prepared to fight in Afghanistan and Syria and Libya and eastern Ukraine as readily as we would fight for a NATO ally.

Compared with that vision, the Trump doctrine aims for a more limited and sustainable view of American commitments. Along with jihadism it seeks to confront and contain two major state-based enemies, China and Iran, and it takes a harsh line toward their potential allies and clients in the Americas. But it has no nation-building ambitions in the Muslim world, no dreams of pushing NATO into the Caucasus, and in East Asia it’s trying to woo the Kim regime into some kind of bizarre friendship instead of acting like Pyongyang is just as great a long-term danger as its patron in Beijing.

The administration’s official European goals (if not Trump’s behind-the-scenes anti-NATO grumbling) also fit plausibly into its larger framework: Building up a stronger military presence on NATO’s Russia-facing flank while getting other countries to bear more of the military burden is the most plausible way to preserve the Western alliance’s basic purposes while the United States refocuses on China. And in the long run, Trump’s dream (whatever its motivations) of a better working relationship with Russia also fits with a retrench-and-refocus framework — with the major caveat that Putin seems too interested in disruption to make a genuine and cooperative détente imaginable for now.

Let me stress that I don’t think that Trump’s grand strategy is springing fully formed from the president’s own mind (he isn’t scribbling notes about the Monroe Doctrine, I assume), or for that matter anyone else’s; instead it’s emerging organically as a synthesis of his own blustering, quasi-isolationist impulses and the more hawkish and internationalist and status-quo-oriented views of the people working for him. That makes it interesting for future international-relations scholars to study — but also vulnerable to sudden changes of personnel or presidential mood. (If we unleash a ground war in Venezuela tomorrow in a fit of Trumpian pique, you can disregard this column’s analysis.)

And of course it has other vulnerabilities as well. Events often destroy even well-thought-through grand strategies, and every foreign-policy maneuver carries risks. The hawks who fear that jihadism will surge if we pull back from Afghanistan and Syria could be vindicated. So could the institutionalists who fear that Trump’s bluster is damaging our standing and disillusioning our friends, and the human rights activists who regard this administration’s cynicism as a carte blanche for thugs and dictators, and the simple Trump-fearers (like myself) who worry that he could make a truly catastrophic blunder should, say, the North Korea negotiations blow up or a real crisis with Russia or China comes along.

But those of us who fear Trump also need to be honest when he exceeds our expectations. Before his election, I wanted a Republican foreign policy that was less hubristic and more calculating than what most leading G.O.P. politicians were offering, that showed a willingness to limit foreign interventions and conduct diplomatic experiments while also trying to maintain United States primacy in a more multipolar, Chinese-influenced world.

Within certain limits, and with a lot of stumbling and bluster, that’s roughly what Trump has delivered. And however his foreign policy looks by November 2020, I suspect that future administrations of both parties will often find themselves imitating the strategy of his first two years.

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