The US can't deter a Russian invasion of Ukraine — and shouldn't even try

The first rule of international relations is that the strong do what they will and the weak suffer what they must. The second rule is that, most of the time, not even superpowers can change the first rule. Unfortunately, advocates of a strong U.S. security commitment to Ukraine seem not to understand these rules. They believe instead that Washington can somehow prevent strong Russia from doing what it will with weak Ukraine. But this is a fantasy. The harsh reality is that Washington can’t deter a Russian invasion of Ukraine — and shouldn’t even try.

The problem is that there is no commitment that the U.S. can credibly make to Kyiv that will raise the costs of invasion to the point where Russia will back off. Moscow’s interests in Ukraine are effectively existential. After the fall of the Soviet Union, Russia’s leaders came to believe that the eastward expansion of NATO posed a serious security threat to the Russian state.

Moreover, Moscow came to view the eastward expansion of the EU as a threat to its vision of a post-Soviet economic space — a Eurasian Economic Union centered on Russia but including other former Soviet republics in Europe as well. As a result, they sought assurances that Ukraine in particular would be incorporated into neither NATO nor the EU.

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But such assurances as were forthcoming were hollow. NATO was ultimately expanded eastward to include not merely former Warsaw Pact countries such as Poland and Hungary but also the former Soviet republics of Latvia, Lithuania and Estonia. Similarly, the EU came to include several eastern European countries that had formerly been in Moscow’s political and economic orbit.

Faced with this, and the prospect that the process would continue right up to Russia’s doorstep, Moscow drew a bright red line on the map: NATO and the EU could not be allowed to expand beyond Ukraine’s western border. Efforts to expand either manifestation of “the West” beyond this line would be considered a threat to Russia’s core national security interests and treated as a casus belli, an act justifying war.

And so, when it seemed as if that warning would not be heeded and Ukraine might enter into an Association Agreement with the EU, Russia struck out, first invading Crimea in 2014 then intervening in the Donbas region of eastern Ukraine. Moscow’s goal both times was nothing more or less than preventing Ukraine from falling further into the Western orbit or, failing that, to carve out a buffer zone along Russia’s western frontier. 

Having acted once before, there is no reason to believe that Moscow would not take military action again if it felt that the situation on that frontier were deteriorating once again. For Russia, the stakes are existential — Ukraine must be kept from becoming part of the West or Russia’s very existence will be threatened. As far as we can reasonably infer from its words and actions, Moscow is therefore willing to tolerate and risk war – even war with the U.S. – over Ukraine in a way that it wouldn’t over any other territory on its periphery. Simply put, if Russia is to be deterred from attacking Ukraine, the costs of such an attack would have to be made very high indeed.

And there is no way that the U.S. will impose such costs. To be sure, Washington may threaten economic sanctions and various acts of political censure in response to a Russian attack on Ukraine. But Russia has endured such costs since its annexation of Crimea and has learned to live with them. The U.S. may be able to impose an additional modicum of economic pain on Russia. But given Moscow’s resolve in this matter, such an incremental increase in economic suffering is hardly likely to prove decisive.

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That leaves the military costs. In order to deter Moscow, the U.S. must have the military capability to defeat Russia swiftly and decisively and the political resolve to do so. Despite the persistent myth of Russian military decline, however, it is not clear that U.S. forces would be able to win a swift and decisive victory in Ukraine. The Russian military is a well-equipped, experienced combat force with a proven ability to fight conventional and hybrid wars. No one doubts that, at a minimum, it could inflict substantial casualties on the U.S military should it enter the conflict. It might even emerge victorious.

And such a conflict would be complicated by geography. Given the proximity of Russia to the likely theater of conflict, it would be impossible for the United States to prevail without suppressing Russian missiles and other assets positioned in Russia. As any such efforts might be mistaken for a first-strike intended to degrade Moscow’s nuclear deterrent (and in any case would be considered an attack on the homeland), the prospects for escalation to nuclear war cannot be discounted.

Similarly, if Moscow felt itself on the verge of defeat in a conflict considered existential, it might resort, in extemis, to the use of nuclear weapons. Either way, the risks of escalation to nuclear war are real. 

Washington, of course, might well run such risks in a confrontation where its core security interests were at stake. But no such interests are at stake in Ukraine. A neutralized Kyiv – or even one firmly in Russia’s geopolitical orbit – poses no threat to American prosperity, security or freedom. Indeed, to the extent that it addressed Russian insecurities, such an outcome might actually reduce tensions between the two powers.

In sum, Russian resolve to neutralize Ukraine – by military means if necessary – will always exceed Washington’s resolve to secure Ukraine. This means that the U.S. can’t deter Russia. And that in turn means that the Biden administration would be well advised to stop making promises it can’t keep to Kyiv, to accept that Ukraine will never be fully incorporated into the West and to be a little more restrained in its geopolitical aspirations in a part of the world that is simply not of great importance to U.S. national security. 

Andrew Latham is a professor of international relations at Macalester College in St. Paul, Minn. and a non-resident fellow at Defense Priorities in Washington, D.C.