AFTER THE Soviet Union collapsed, Richard Nixon observed that the United States had won the Cold War, but had not yet won the peace. Since then, three American presidents—representing both political parties—have not yet accomplished that task. On the contrary, peace seems increasingly out of reach as threats to U.S. security and prosperity multiply both at the systemic level, where dissatisfied major powers are increasingly challenging the international order, and at the state and substate level, where dissatisfied ethnic, tribal, religious and other groups are destabilizing key countries and even entire regions.

Most dangerous are disagreements over the international system and the prerogatives of major powers in their immediate neighborhoods—disputes of the sort that have historically produced the greatest conflicts. And these are at the core of U.S. and Western tensions with Russia and, even more ominously, with China. At present, the most urgent challenge is the ongoing crisis in Ukraine. There, one can hear eerie echoes of the events a century ago that produced the catastrophe known as World War I. For the moment, the ambiguous, narrow and inconsistently interpreted Minsk II agreement is holding, and we can hope that it will lead to further agreements that prevent the return of a hot war. But the war that has already occurred and may continue reflected deep contradictions that America cannot resolve if it does not address them honestly and directly.

In the United States and Europe, many believe that the best way to prevent Russia’s resumption of its historic imperial mission is to assure the independence of Ukraine. They insist that the West must do whatever is required to stop the Kremlin from establishing direct or indirect control over that country. Otherwise, they foresee Russia reassembling the former Soviet empire and threatening all of Europe. Conversely, in Russia, many claim that while Russia is willing to recognize Ukraine’s sovereignty and territorial integrity (with the exception of Crimea), Moscow will demand no less than any other great power would on its border. Security on its western frontier requires a special relationship with Ukraine and a degree of deference expected in major powers’ spheres of influence. More specifically, Russia’s establishment sentiment holds that the country can never be secure if Ukraine joins NATO or becomes a part of a hostile Euro-Atlantic community. From their perspective, this makes Ukraine’s nonadversarial status a nonnegotiable demand for any Russia powerful enough to defend its national-security interests.

When the Soviet Union collapsed in 1991, Russia was on its knees, dependent on Western assistance and consumed by its own internal affairs. In that context, it was not surprising that Western leaders became accustomed to ignoring Russian perspectives. But since Vladimir Putin took over in 1999, he has led a recovery of Russia’s sense of itself as a great power. Fueled by rising oil production and prices that brought a doubling of Russia’s GDP during his fifteen-year reign, Russians increasingly bridled at such treatment.

Americans would do well to recall the sequence of events that led to Japan’s attack on the United States at Pearl Harbor and America’s entry into the Second World War. In 1941, the United States imposed a near-total embargo on oil shipments to Japan to punish its aggression on the Asian mainland. Unfortunately, Washington drastically underestimated how Japan would respond. As one of the post–World War II “wise men,” Secretary of State Dean Acheson, observed afterward, the American government’s

misreading was not of what the Japanese government proposed to do in Asia, not of the hostility our embargo would excite, but of the incredibly high risks General Tojo would assume to accomplish his ends. No one in Washington realized that he and his regime regarded the conquest of Asia not as the accomplishment of an ambition but as the survival of a regime. It was a life-and-death matter to them.

Just days before Pearl Harbor, Japanese special envoy Saburo Kurusu told Washington that “the Japanese people believe that economic measures are a much more effective weapon of war than military measures; that . . . they are being placed under severe pressure by the United States to yield to the American position; and that it is preferable to fight rather than to yield to pressure.” Despite this warning, the Japanese response to U.S. economic warfare caught the United States off guard, killing nearly 2,500 people and sinking much of the U.S. Pacific Fleet.

Reviewing the recent record of American administrations’ forecasts about the consequences of major foreign-policy choices should serve as a bright warning light. The Clinton administration misread an extended and bloody civil war in Yugoslavia before imposing its own shaky partition and angering Russia and China in the process. When George W. Bush decided to invade Iraq and replace Saddam Hussein’s regime with a democratically elected one, he believed that this would, as he said, “serve as a powerful example of liberty and freedom in a part of the world that is desperate for liberty and freedom.” He and his team held firmly to this conviction, despite numerous warnings that war would fragment the country along tribal and religious lines, that any elected government in Baghdad would be Shia-dominated and that Iran would be the principal beneficiary from a weakened Iraq. Next, the Obama administration joined Britain and France in a major air campaign in Libya to remove Muammar el-Qaddafi. The consequent chaos contributed to the killings of a U.S. ambassador and other American diplomats and to the creation of a haven for Islamic extremists more threatening than Qaddafi’s Libya to its neighbors and to America. In Syria, at the outset of the civil war, the Obama administration demanded the ouster of President Bashar al-Assad, even though he never posed a direct threat to America. Neither the Obama administration nor members of Congress took seriously predictions that Islamic extremists would dominate the Syrian opposition rather than more moderate forces—and that Assad would not be easy to displace.

COULD A U.S. response to Russia’s actions in Ukraine provoke a confrontation that leads to a U.S.-Russian war? Such a possibility seems almost inconceivable. But when judging something to be “inconceivable,” we should always remind ourselves that this is a statement not about what is possible in the world, but about what we can imagine. As Iraq, Libya and Syria demonstrate, political leaders often have difficulties envisioning events they find uncomfortable, disturbing or inconvenient.

Prevailing views of the current confrontation with Russia over Ukraine fit this pattern. Since removing Slobodan Milosevic, Saddam Hussein and Muammar el-Qaddafi from power had limited direct impact on most Americans, it is perhaps not surprising that most Washington policy makers and analysts assume that challenging Russia over Ukraine and seeking to isolate Moscow internationally and cripple it economically will not come at a significant cost, much less pose real dangers to America. After all, the most common refrain in Washington when the topic of Russia comes up is that “Russia doesn’t matter anymore.” No one in the capital enjoys attempting to humiliate Putin more than President Barack Obama, who repeatedly includes Russia in his list of current scourges alongside the Islamic State and Ebola. And there can be no question that as a petrostate, Russia is vulnerable economically and has very few, if any, genuine allies. Moreover, many among its business and intellectual elites are as enthusiastic as the Washington Post editorial page to see Putin leave office. Ukrainians with the same view of former Ukrainian president Viktor F. Yanukovych successfully ousted him with limited Western help, so, it is argued, perhaps Putin is vulnerable, too.

Nevertheless, Russia is very different from the other countries where the United States has supported regime change. First and most important, it has a nuclear arsenal capable of literally erasing the United States from the map. While many Americans have persuaded themselves that nuclear weapons are no longer relevant in international politics, officials and generals in Moscow feel differently. Second, regardless of how Americans view their country, Russians see it as a great power. Great powers are rarely content to serve simply as objects of other states’ policies. Where they have the power to do so, they take their destiny into their own hands, for good or ill.

WHILE MOST policy makers and commentators dismiss the possibility of a U.S.-Russian war, we are more concerned about the drift of events than at any point since the end of the Cold War. We say this having followed Soviet and Russian affairs throughout the Cold War and in the years since the Soviet Union’s implosion in 1991. And we say it after one of us recently spent a week in Moscow talking candidly with individuals in and around the Putin government, including with many influential Russian officials, and the other in China listening to views from Beijing. We base our assessment on these conversations as well as other public and private sources.

There are three key factors in considering how today’s conflict might escalate to war: Russia’s decision making, Russia’s politics and U.S.-Russian dynamics.

With respect to Russia’s decision making, Putin is recognized both inside and outside the country as the unilateral decider. All available evidence suggests that he relies on a very narrow circle of advisers, none of whom is prepared to challenge his assumptions. This process is unlikely to help Putin make informed decisions that fully take account of the real costs and benefits.

Moreover, Russia’s political environment, at both the elite and public levels, encourages Putin to escalate demands rather than make concessions. At the elite level, Russia’s establishment falls into two camps: a pragmatic camp, which is currently dominant thanks principally to Putin’s support, and a hard-line camp. The Russian public largely supports the hard-line camp, whom one Putin adviser called the “hotheads.” Given Russian politics today, Putin is personally responsible for the fact that Russia’s revanchist policies are not more aggressive. Put bluntly, Putin is not the hardest of the hard-liners in Russia.

While none of the “hotheads” criticize Putin, even in private conversations, a growing number of military and national-security officials favor a considerably tougher approach to the United States and Europe in the Ukraine crisis. This is apparent in their attacks on such relatively moderate cabinet officers as Vice Prime Minister Igor Shuvalov and Foreign Minister Sergey Lavrov. From their perspective, the moderates fail to comprehend the gravity of the U.S.-European challenge to Russia and hold futile hopes that things can change for the better without Russia surrendering to an unacceptable and degrading foreign diktat. They recommend shifting the game to areas of Russian strength—by using military force to advance Russian interests as Putin did in Crimea and to pressure the West into accepting Moscow on its own terms.

An increasingly nationalistic Russian public also supports this “challenge the main enemy” approach, which draws its language and inspiration from former Soviet leader Yuri Andropov. Putin has clearly contributed to growing nationalist sentiments through his patriotic rhetoric and his harsh indictment of Western behavior. But he was pushing on an open door due to widespread disillusionment with Western treatment of Russia as a Cold War loser rather than an ally in building a new world order. What’s more, ordinary Russians may have gone further in their truculent views than Putin himself. Not long ago, Russia’s media widely reported a warning from the recently dismissed rebel commander Igor Strelkov, who said that by being too indecisive, Putin would satisfy no one and would suffer the same fate as Slobodan Milosevic—rejection by liberals and nationalists alike. More recently, Strelkov has reportedly placed Putin’s portrait prominently in his office, explaining that in his view the Russian president “understood that all compromise with the West is fruitless” and that he is “reestablishing Russian sovereignty.” Strelkov often exaggerates, but his views reflect the frustrations of Russia’s influential nationalist coalition.

Added support for a more muscular assertiveness comes from an expanding group of military officers and civilians who believe that Russia can brandish its nuclear weapons to good effect. According to this group, Russia’s nuclear arsenal is not just its ultimate security blanket but also a sword it can wield to coerce others who have no nuclear weapons, as well as those who are unwilling to think the unthinkable of actually exploding a nuclear bomb. Putin appeared to endorse this view in his controversial Sochi speech last September when he said:

Nikita Khrushchev hammered the desk with his shoe at the UN. And the whole world, primarily the United States and NATO, thought, “This Nikita is best left alone, he might just go and fire a missile. We better show some respect for them.” Now the Soviet Union is gone and there is no need to take into account Russia’s views. It has gone through transformation during the collapse of the Soviet Union, and we can do whatever we like, disregarding all rules and regulations.

The director of the television network Rossiya Segodnya, Dmitry Kiselyov, has been more explicit, repeatedly warning, “Russia is the only country in the world that is realistically capable of turning the United States into radioactive ash.” Russia’s 2014 Military Doctrine emphasizes that Russia will use nuclear weapons not only in response to nuclear attacks but also “in the case of aggression against the Russian Federation with the use of conventional weapons.” And, as a recent report of the European Leadership Network notes, there have been almost forty incidents in the past year in which Russian forces engaged in a pattern of provocations that, if continued, “could prove catastrophic.”

Counterintuitive though it may seem, Russia’s weakening economy is also unlikely to create public pressure for concessions. On the contrary, the damage to an already-stagnant Russian economy suffering from low energy prices is actually reducing Putin’s foreign-policy flexibility. Russia’s president needs to show that his country’s suffering has been worth it. Retreat could severely damage Putin’s carefully cultivated image as a strong man—a style Russians have historically appreciated—and alienate his hypernationalist political base. They resent sanctions, which they see as hurting ordinary people much more than Putin’s entourage, and they want their leaders to resist, not capitulate. For many, Russia’s dignity is at stake.

This came through clearly in a recent conversation with a top Russian official. When asked why his government would not try to negotiate a deal based on principles it has already articulated, such as exchanging Russian guarantees of Ukraine’s territorial integrity minus Crimea and Ukraine’s right to move toward the European Union for Western guarantees that Ukraine would not join NATO and that the United States and the European Union would relax sanctions, the official responded by saying, “We have our pride and cannot appear to be pressuring the insurgents to have sanctions reduced.”

THE KEY question is this: Will Putin continue to support the relatively moderate pragmatists, or will he turn toward the “hotheads”? So far, he has split the difference: Russia has provided effective but limited support to the separatists, while at the same time hoping against hope to restore many of its ties with the West (or at least with Europe). Putin has also tried to conceal the scale of Russia’s intervention in order to temporize and to exploit U.S.-European and intra-European differences.

Currently, the pragmatists retain the upper hand, in no small part because Putin has kept his government team almost intact both in the cabinet and in the presidential administration. While loyal to Putin and prepared to execute his agenda, that team consists primarily of officials whose formative experiences have been in establishing economic interdependence with the West and in attempting to make Russia a major voice in a world order predominantly shaped by the United States and its allies.

Foreign Minister Lavrov and others supporting his more pragmatic approach argue that Moscow can still do business with the United States and especially with the Europeans if Russia doesn’t close the door. The “hotheads” take the opposite view, insisting that the West would view any moderation in Russian policy as a sign of weakness. Portraying themselves as realists, they argue that NATO is determined to overthrow Putin, force Russia to its knees and perhaps even dismember the country.

Putin’s reluctance to change course dramatically so far explains his hybrid war in eastern Ukraine, which helps the separatists without Russia formally entering the conflict. It also underlies Russia’s unpersuasive denials that it is giving military support to the separatists, which simultaneously make Moscow subject to justified criticism and create unfounded hope in Washington and in Europe that Russia will be unable to absorb higher casualties in a war in which it claims not to participate.

Yet Putin’s attempt to pursue the pragmatists’ broad objectives while accommodating the “hotheads” on the ground in Ukraine may not be indefinitely sustainable. An increasingly prevalent view among Putin’s advisers sees hopes of a restoration of Western-Russian cooperation as a lost cause because U.S. and Western leaders will not accept any resolution that meets Russia’s minimal requirements. If the United States and the European Union would largely remove sanctions and restore business as usual, they would urge that Russia swallow its pride and reconcile. But if Russia is going to continue to be sanctioned, excluded from financial markets and denied Western technology, they say, then Russia should pursue its own independent path. Putin has yet to face a decisive moment that would require him to make a fateful choice between accommodating Western demands and more directly entering the conflict and perhaps even using force against Western interests outside Ukraine. And if that moment arrives, we may well not welcome his choice.

SANCTIONS ASIDE, two other developments could force Putin’s hand. One would be the prospect of military defeat of the separatists; the second would be NATO membership for Ukraine.

Putin drew a bright red line precluding the first in an interview with Germany’s ARD television channel on November 17, 2014. Speaking rhetorically, he asked whether NATO wanted “the Ukrainian central authorities to annihilate everyone among their political foes and opponents” in eastern Ukraine. If so, Putin declared categorically: “We won’t let it happen.” In every instance when the Ukrainian military seemed close to gaining the upper hand in the fighting, and despite U.S. and European warnings and sanctions, Putin has raised the ante to assure the separatists’ success on the battlefield.

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.

LATVIA, ESTONIA, and Lithuania form the Achilles’ heel of the NATO alliance. They are protected by its Article 5 guarantee that an attack upon one will be regarded as an attack upon all. Thus, the United States has an unambiguous and undeniable responsibility to deter and defend attacks on the Baltic states. Given their size, proximity to Russia and substantial Russian-speaking minorities, this is a daunting requirement. It is not difficult to imagine scenarios in which either U.S. or Russian action could set in motion a chain of events at the end of which American and Russian troops would be killing each other.

There is currently a lively discussion among Russian hard-liners about how Russian dominance in both conventional forces and tactical nuclear weapons in Central and Eastern Europe could be used to Russia’s advantage. Putin has talked publicly about his willingness to use nuclear weapons to repel any effort to retake Crimea—noting that he relied on Russia’s nuclear arsenal during the Crimean operation. In these debates, many ask whether President Obama would risk losing Chicago, New York and Washington to protect Riga, Tallinn and Vilnius. It is a troubling question. If you want to either dumbfound or silence a table next to you in a restaurant in Washington or Boston, ask your fellow diners what they think. If stealthy Russian military forces were to take control of Estonia or Latvia, what should the United States do? Would they support sending Americans to fight for the survival of Estonia or Latvia?

Imagine, for example, an uprising of ethnic Russians in Estonia or Latvia, either spontaneously or at the instigation of Russian security services; a heavy-handed response by that nation’s weak police and military forces; an appeal by ethnic Russians to Putin to honor his “Putin Doctrine” declaration during the liberation of Crimea that he would come to the defense of ethnic Russians wherever they were attacked; an attempted replay of the hybrid war against Ukraine; and a confrontation with the battalion of six hundred American or NATO forces now on regular rotations through the Baltic states. Some Russians have gone so far as to suggest that this would provide sufficient provocation for Moscow to use a tactical nuclear weapon; Russia’s ambassador to Denmark, for example, recently threatened that Danish participation in NATO’s missile-defense system would make it “a target for Russian nuclear weapons.” What’s more, Russia is exploring stationing Iskander missiles in Kaliningrad—the Russian enclave between Lithuania and Poland—while Sweden’s intelligence has publicly stated that it views Russian intelligence operations as preparation for “military operations against Sweden.”

IN A climate of mutual suspicion further fueled by domestic politics on both sides, assurances of benign intentions rarely suffice. Christopher Clark’s 2013 book, The Sleepwalkers, provides a persuasive account of how, in the days preceding World War I, both alliances contemptuously dismissed the explanations and assurances they heard from the other side.

Of course, alliances are now Putin’s weakest point. Russia does not have a single ally committed to supporting Moscow in war. Nevertheless, one should be cautious about counting on Moscow’s isolation in a longer-term confrontation with the West. One reason Kaiser Wilhelm II presented his ultimatum to Russia was that he did not believe England would join Russia in a war over the crisis in the Balkans, where London had traditionally opposed Russian influence. Furthermore, without England, few expected France to offer much resistance. What those who count on Russian isolation today do not properly take into account is that a powerful and assertive alliance prepared to pursue its interests and promote its values inevitably stimulates antibodies. It was that sense of Germany’s determination to change the geopolitical balance in Europe and in the world that prompted Britain to depart from a century of splendid isolation and become so entangled with allies that when war came, it had little choice but to enter. It is the same sense that is leading China today to expand its ties with Russia during its conflict with the United States.

To be clear, there is virtually no chance that China would join Russia against the United States and Europe in a confrontation over Ukraine. Likewise, China is not prepared to bail Russia out financially or to risk its lucrative economic integration with the West to support Moscow’s revanchist ambitions. But neither is Beijing indifferent to the possibility of Russia’s political, economic or (particularly) military defeat by the Western alliance. Many in Beijing fear that if the United States and its allies were successful in defeating Russia, and particularly in changing the regime in Russia, China could well be the next target. The fact that the Chinese leadership views this as a serious threat could, over time, push Beijing closer to Moscow, a development that would fundamentally alter the global balance of power.

Moreover, if there were a Russian-American war, one needs to think carefully about what actions the Chinese might choose to take against Taiwan, for example, or even to punish neighbors like Japan or Vietnam whom Beijing believes are cooperating with Washington to contain its ambitions.

Neither China nor Russia is the first state to confront a powerful and growing alliance. Nor is the United States the first to receive enthusiastic appeals from prospective allies that can add marginally to overall capabilities, but simultaneously bring obligations and make others feel insecure. In a timeless passage in his History of the Peloponnesian War, Thucydides recounts the Athenian response to a troubled Sparta: “We did not gain this empire by force. . . . Our allies came to us of their own accord and begged us to lead them.” Needless to say, Sparta did not find that explanation reassuring—and that excuse did not prevent thirty years of war that ended with defeat for Athens, but at a price far beyond any benefits that accrued to the victor.

To recognize the potentially catastrophic consequences of war with Russia does not require paralysis in addressing the challenge of a resurgent but wounded Russia. The United States has a vital interest in maintaining its credibility as a superpower and in assuring the survival and security of its NATO alliance—and thus of every one of its NATO allies. Moreover, in international politics, appetites can grow quickly if fed by easy victories.

The Russian president’s currently limited objectives in Ukraine could become more expansive if Russia does not face serious resistance. After all, the smooth annexation of Crimea led to an outburst of triumphalist rhetoric in Moscow about creating a new entity, Novorossiya, which would include eastern and southern Ukraine all the way to the Romanian border. The combination of resistance by local populations, the Ukrainian government’s willingness to fight for its territory, and U.S. and EU sanctions quickly persuaded the Russian leadership to curtail this line of thinking. When a nation is prepared to fight for important interests, clarity about that determination is a virtue in discouraging potential aggression.

Yet the United States should be careful to avoid giving allies or friends—like Kiev—the sense that they have a blank check in confronting Moscow. During World War I, even such a strong supporter of the war as Pavel N. Milyukov—leader of Russia’s Constitutional Democrats and later foreign minister in the Provisional Government—was shocked at the lengths to which British foreign secretary Sir Edward Grey would go in refusing to assign any blame for the conflict to the Serbs. “Listen,” he reports saying to Grey, “the war started because of Serb grandstanding. Austria could think that it was in serious danger. Serbia was aspiring to do no less than to split Austria.” To Grey, however, an ally could do no wrong.

The Balkan crises in the several years prior to World War I deserve careful study. Few at the time could conceive that they would become the flashpoint of a fire that would eventually become a continental inferno.

But they did. Meeting the challenge of an angry but weakened Russia today requires a subtle combination of firmness and restraint. Where vital American interests are engaged, we have to be able and willing to fight: to kill and to die. Effective deterrence requires three C’s: clarity about red lines that cannot be crossed (for example, attacking a NATO ally); capability to respond in ways that will make the cost of aggression greatly exceed any benefits an aggressor could hope to achieve; and credibility about our determination to fulfill our commitment. At the same time, we should recognize that if American and Russian forces find themselves firing upon each other, this would violate one of the principal constraints both sides respected assiduously during four decades of the Cold War—risking escalation to a war both would lose.

Military force and economic warfare such as sanctions are indispensable instruments of foreign policy. When employed without a sound strategic vision and artful diplomacy, however, instruments of coercion can develop their own momentum and become ends in themselves. Having managed a confrontation over the Soviet Union’s attempt to install nuclear-tipped missiles in Cuba that he believed had a one-in-three chance of ending in nuclear war, President John F. Kennedy spent many hours reflecting on the lessons from that experience. The most important of these he offered to his successors in these words: “Above all, while defending our vital interests, nuclear powers must avert those confrontations which bring an adversary to a choice of either a humiliating retreat or a nuclear war.” It is a lesson statesmen should apply to meet the challenge Russia poses in Ukraine today.

Graham Allison is director of the Harvard Kennedy School’s Belfer Center for Science and International Affairs and a former assistant secretary of defense for policy and plans. Dimitri K. Simes, The National Interest’s publisher, is president of the Center for the National Interest.

Image: Wikimedia Commons/Rob Schleiffert