President Trump has changed his mind on many issues. Yet there is one theme of his presidency that remains strikingly constant: his peculiar deference to his Russian counterpart Vladimir Putin. We witnessed it again in Trump’s new interview with Jonathan Swan of Axios, when he once again refused to criticize the Russian president for allegedly offering Taliban fighters bounties in return for killing U.S. soldiers, and also excused Russian arming of the Taliban by arguing, “Well, we sold them weapons when they were fighting Russia, too. The Taliban, in Afghanistan. … I’m just saying, we did that, too.” (Note: The Taliban, which was formed in 1994, never fought Soviet forces, which left the country five years earlier.) We already knew that Trump had avoided raising the issue in a series of phone calls with Putin in the past few months.

Trump’s stubborn refusal to criticize Putin remains a mystery. But the damage this position has done to U.S. interests is known, and could become even greater in the future. Most troubling, Trump’s stance on Putin — which often contrasts with policies of his own administration — creates an ambiguity that is destructive in his own right.

We learned during the Cold War about the dangers of uncertainty. Joseph Stalin misread Harry S. Truman when he tried to choke off Berlin in 1948. After their meeting in Vienna in June 1961, Khrushchev underestimated Kennedy’s resolve, a miscalculation that helped to precipitate the Cuban missile crisis months later.

Let’s imagine, just for a moment, that Trump wins reelection in November. He will then be able to claim that American voters have ratified his foreign policy instincts — instincts that already have included a weakened commitment to our NATO allies and an unwavering embrace of Putin. These signals of weakness might tempt Putin to probe the credibility of Trump’s commitment to NATO.

What if, for instance, Putin orders Russian special operations forces into Estonia to attack a handful of people based on some fabricated pretext (such as the killing or harming of ethnic Russians living in Estonia) — and then withdraws? Or what if Putin proxies succeed in executing a coup — something they’ve apparently already tried once — in Montenegro, a NATO member? Will Trump come to the aid of our NATO allies? Maybe. Maybe not.

It is the very ambiguity of Trump responses that is destabilizing. Given the complete lack of response to Putin’s past aggressions, coupled with open hostility toward NATO, Putin might assume with good reason that Trump will do nothing. If Putin calculates correctly, the future of NATO is on the line; if Putin calculates incorrectly, conventional war in Europe could unintentionally result. Thankfully, these scenarios are not probable. Tragically and scarily, as long as Trump remains in the White House, they also are not completely improbable.

Though Trump’s unqualified embrace of a Russian dictator is unprecedented, he is not the first American president to try to forge a personal bond with a Russian leader. Trump may well believe that a “good relationship” with Putin is a worthy goal in itself, rather than as a means for securing some concrete benefit for the American people.

And yet, though he claims to be transactional, Trump has not completed a single noteworthy transaction with the Russian president. The two leaders have not signed a nuclear arms control deal or even extended the existing New START Treaty, set to expire next February. Putin has not helped Trump prevent Iran from obtaining a nuclear weapon, nor aided Trump’s diplomacy with North Korea. Putin is clearly not facilitating U.S. diplomatic and military objectives in Afghanistan. In our conflicts with China, Putin sides with President Xi Jinping. Trump has not succeeded in ending Putin’s support for insurgents in eastern Ukraine, but instead has done major damage to U.S.-Ukraine relations by pressuring the Ukrainian government to aid his reelection campaign.

The United States and Russia have signed no trade deals. Trump has not succeeded in persuading his Russian friend to allow Americans to adopt Russian orphans again, or to release falsely convicted Paul Whelan from a Russian prison. Last week, former U.S. marine Trevor Reed was sentenced to nine years in jail on the flimsiest of evidence. To the best of our knowledge, Trump has never raised this improper treatment of an American citizen with Putin.

It gets worse. Trump has made several foreign policy decisions that benefit Putin. Last year he ordered U.S. soldiers to leave Syria, allowing Putin to claim a military victory in Russia’s fight against terrorism there. This year, Trump suggested that Russia attend the Group of 7 summit planned for 2020 in the United States, a decision that no other G-7 leader supported. Last month, Trump made official his decision to withdraw 12,000 American troops from Germany.

Given this consistent track record of supporting Putin, it should not be surprising that Putin might misjudge Trump’s commitment to NATO or deterrence more generally. Trump’s latest signal of weakness — refusal to even raise the issue of Russian actions against U.S. soldiers in Afghanistan — can only deepen Putin’s doubts about American resolve. Such doubts in turn can birth dangerous adventurism.

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