Though Russia’s president has said less about the second red line, there can be no doubt that Ukraine’s potential NATO membership is a preeminent Russian concern. One important reason for Moscow’s willingness to let Donetsk and Luhansk go back under central Ukrainian control with a considerable degree of autonomy is the Kremlin’s desire for their pro-Russian populations to vote in Ukrainian elections and for their autonomous local governments to serve as a brake on Ukraine’s road to NATO. Russia’s political mainstream overwhelmingly supports preventing the emergence of a hostile Ukraine under NATO security umbrella less than four hundred miles from Moscow.

This feeling is grounded both in Russian security concerns and in nearly uncontrollable sentiments about Ukraine and its Russian-speaking population. The growing popularity of the slogan Rossiya ne brosayet svoikh—Russia does not abandon its own—reflects these feelings and resembles Russia’s pan-Slavic attitudes toward Serbia before World War I. One of us saw a powerful example of these emotions while watching a Russian talk-show discussion about Ukraine before a live audience. A Russian panelist declared that “our cause is just and we will prevail” to thunderous applause. Importantly, the speaker, Vyacheslav Nikonov, is not only a member of the pro-Putin United Russia party and the chairman of the parliament’s education committee. He is also the grandson of former Soviet foreign minister Vyacheslav Molotov, who made the same statement after Hitler attacked the USSR in 1941. Nikonov is known for reflecting establishment perspectives. The early nineteenth-century Savoyard diplomat and conservative philosopher Joseph de Maistre saw something similar in his own time: “There is no man who desires as passionately as a Russian. If we could imprison a Russian desire beneath a fortress, that fortress would explode.” Russian nationalism today is such an explosive force.

Little imagination is required to find possible triggers for a decisive change in Putin’s posture. The most immediate would be a U.S. decision to arm Ukraine’s military. Could some in Putin’s government actually be seeking to entice the United States into arming Ukraine? While this seems far-fetched at first blush, another Russian interlocutor made a thoughtful case that this is indeed the plan of some around Putin, perhaps even with Putin’s consent. According to this theory, this ploy has both a tactical and a strategic rationale.

Tactically, an announcement by Obama that the United States was sending arms to Ukraine would give Putin an easy escape from what has become an increasingly untenable denial of the obvious. To fellow Russian citizens, Putin and his government have unambiguously and repeatedly insisted that Russia is not a party to the conflict, despite the fact that pro-Russian government politicians and separatist leaders brag about Moscow’s help on television. Even after the downing of the Malaysian airliner killed nearly three hundred last July, and despite continuous Western reporting of the facts, Putin has stuck to his story.

An announcement that Washington was arming Ukraine would, it is argued, give Putin the pretext he needs to affirm his narrative. He has claimed that the United States sponsored the Maidan coup that ousted Yanukovych, a democratically elected president, and has been supporting the current government’s war against fellow Russians in eastern Ukraine. Overtly arming Ukraine will thus unmask previously covert American activity and justify Russia responding with arms or even troops, initiating a game of escalation that plays to his strength.

Strategically, this would be what chess masters call a trap. By shifting the competition from the economic chessboard (where the United States and Europe have all the powerful pieces) to a military one, he will have moved from weakness to strength. In the military arena, Putin owns the commanding heights: there is hardly a weapon the United States can provide Kiev that Russia can’t match or trump; logistically, he can send arms by road, rail, sea and air across a porous border, while the United States is a continent away; within the ranks of Ukraine’s military, he has hundreds or even thousands of agents and collaborators. And, most importantly, as he has already demonstrated, the Russian military forces are prepared not only to advise separatists but also to fight alongside them—and to kill and to die. He assumes that the United States will never put boots on the ground in Ukraine. The more vividly he can drive this home to Europeans, so hard-line thinking goes, the more respect he can command.

Hard-liners see this as Putin’s best chance to snatch what they call “strategic victory” from the jaws of defeat. As they see it, Russia’s comparative advantage in relations with Europe and the United States is not economics. Instead, it is deploying military power. Europeans have essentially disarmed themselves and show little will to fight. Americans undoubtedly have the most powerful military on earth and are often prepared to fight. But even though they win all the battles, they seem incapable of winning a war, as in Vietnam or Iraq. In Ukraine, the “hotheads” hope, Russia can teach the Europeans and Americans some hard truths. The professionally executed operation that annexed Crimea virtually without a shot was the first step. But the deeper the United States can be sucked into Ukraine and the more visibly it is committed to achieving unachievable goals like the restoration of Ukraine’s territorial integrity, the better from this hawkish Russian perspective. On the battlefield of war in Ukraine, Russia has what Cold War strategists named “escalation dominance”: the upper hand at every step up the escalation ladder. This is a proxy war the United States cannot win and Russia cannot lose—unless America is willing to go to war itself.

THE PRIMARY audience for this drama is, of course, Europe. The fact that neither European members of NATO nor the United States can save Ukraine is hoped to sink into the consciousness of postmodern Europeans. When it does, according to this logic, a skillful combination of intimidation and intimation of hope should give Russia an opening to drive a wedge between the United States and Europe, providing relief from the most onerous sanctions and access to European financial markets.

Initially, Putin will attempt to exploit the expiration of EU sanctions, which are scheduled to expire in July. If that fails, however, and the European Union joins the United States in imposing additional economic sanctions, such as excluding Moscow from the SWIFT financial clearing system, Putin would be tempted to respond not by retreating, but by ending all cooperation with the West and mobilizing his people against a new and “apocalyptic” threat to Mother Russia. As a leading Russian politician told us, “We stood all alone against Napoleon and against Hitler. It was our victories against aggressors, not our diplomacy, that split enemy coalitions and provided us with new allies.”

At that point, Putin would likely change both his team and the thrust of his foreign policy. As a senior official said, “The president values loyalty and consistency, so letting people go and announcing fundamental policy changes comes hard to him. But he is a decisive man and when he reaches a decision, he does whatever it takes to get results.” This would mean a significantly more belligerent Russian policy across all issues driven by a narrative about a Western campaign to undermine the regime or indeed to cause the collapse of the country. Among other things, it would likely mean an end to cooperation on projects like the International Space Station, supplies of strategic metals like titanium, dealing with Iran’s nuclear program and stabilizing Afghanistan. In the latter case, this could include not only pressuring Central Asian states to curtail security cooperation with the United States, but also exploiting political differences in the Afghan ruling coalition to support the remnants of the Northern Alliance.

ONCE THE U.S.-Russian relationship enters the zone of heated confrontation, senior military officers on both sides will inevitably play a greater role. As the world saw in the lead-up to World War I, when the security dilemma takes hold, what look like reasonable precautions to one side may well appear as evidence of likely aggression to the other. Clausewitz describes the relentless logic that pushes each side toward “a new mutual enhancement, which, in pure conception, must create a fresh effort towards an extreme.” Commanders have to think in terms of capabilities rather than intentions. This pushes them toward steps that are tactically prudent but that invite strategic misinterpretation.

Predictably, leaders and their military advisers will also miscalculate. Before World War I, Kaiser Wilhelm II did not believe that Russia would dare to go to war because its defeat by Japan less than a decade earlier had demonstrated the Russian military’s incompetence. At the same time, Russian defense minister Vladimir Sukhomlinov was assuring the czar that Russia was ready for battle and that Germany had already decided to attack. As Sukhomlinov said in 1912, “Under any circumstances the war is unavoidable and it is advantageous for us to start it sooner rather than later . . . His Majesty and I believe in the army and know that the war will only bring good things to us.” In Berlin, the German General Staff also argued for quick action, fearing the impending completion of a new network of rail lines that would allow the czar to move Russian divisions rapidly to Germany’s border. After the assassination of Archduke Franz Ferdinand, as the crisis intensified, military commanders in both Russia and Germany rushed not to be the second to mobilize. As the Russian General Staff told Nicholas II, only an immediate and full-scale mobilization would prevent a quick defeat, if not of Russia itself, then at least of France, whose long-term support Russia needed to withstand the German assault.