(CNN) Russia's buildup of troops at its border with Ukraine has created a diplomatic standoff between Russia and the US, the world's two largest nuclear powers.
For a better understanding of how we got to this point, and what could come next, I talked to Michael Kimmage, a professor at the Catholic University of America and a visiting fellow at the German Marshall Fund of the United States. He specializes in US-Russia relations and is a voice for engagement with Russia and a more nuanced view of the country.
Our conversation, conducted by email and lightly edited, is below.
RELATED: The latest on Ukraine and Russia tensions
WHAT MATTERS: Let's start with a very general question. If the Cold War was about US capitalism vs. USSR communism, what is the standoff between Russia and the West about today?
KIMMAGE: It is less sweeping than the Cold War. It is, at its core, a contest for influence in Eastern and Central Europe. The Cold War, by contrast, was defined by the Iron Curtain. The military situation was mostly settled after 1949. That is why ideological conflict (over capitalism and democracy) was so intense; it was the real arena of competition.
Today, there is no Iron Curtain in Europe. There is no clear line dividing Russia from Europe, or Europe from Russia. And in this ambiguous situation there is a stark difference of vision or of worldview.
The United States sees the individual states of Europe as entirely sovereign and as entitled to make their own decisions about security, trade, alliances, etc.
Russia sees itself as having a privileged zone of interest along its western border. For reasons of security and of prestige, Russia demands in this area a combination of influence and deference, and Russia is willing to employ military force where it sees itself as thwarted in this privileged zone.
Ukraine falls right in the middle of this contest, and since 2014 both Moscow and Washington have come to see Ukraine as a barometer of Europe's future.
WHAT MATTERS: Much has been written about a potential fraying of the Western alliance. Germany wants to complete a natural gas pipeline from Russia. France is seeking a more independent Europe. Is this the beginning of the end of the post-World War II NATO alliance?
KIMMAGE: Not at all. The alliance has always been a bit unruly.
For a while, France formally distanced itself from NATO -- during the Cold War. And the early 1980s witnessed massive protests in Germany and elsewhere about US missile deployments in Europe. Both the Vietnam and the Iraq wars elicited major differences of opinion among the many NATO member states. So there's nothing new about differing agendas and approaches within NATO.
Taking a step back, the NATO alliance has really been quite unified since December 2021, when the current crisis kicked into high gear.
It has done three things together: provided a measure of military assistance to Ukraine through training and the contributions of individual NATO states to Ukraine's military preparedness; indicated in no uncertain terms that the war between Ukraine and Russia (now in its eighth year) does not directly concern NATO, since Ukraine is not a member of the alliance, and therefore that NATO itself will not be fighting in Ukraine; and taken seriously the new set of anxieties of Poland, Romania and the Baltic republic, some of which stem from the prospect of a wider war in Ukraine and some from Russia's deployment of troops and hardware in Belarus.
In addition, NATO has communicated to Russia that it will not make concessions. It will not move back to where it was in 1997, as Vladimir Putin has demanded of NATO. It will not close the open-door policy on membership, and it will not rule out the possibly of accepting Ukraine into the alliance. On the substantive issues, NATO has shown an impressive degree of unity in the last three months.
WHAT MATTERS: The US and NATO countries formally rejected Russia's demand that Ukraine be barred from entering NATO. Should NATO still be in the business of expanding into Eastern Europe?
KIMMAGE: In my opinion, NATO should no longer be in the business of expanding into Eastern Europe. This is already NATO's de facto policy regarding Moldova, Ukraine and Belarus, which are the three Eastern European countries that could conceivably join NATO.
Moldova features a frozen conflict, and in Moldova there is a Russian military presence.
Belarus has effectively been annexed by Russia in the last few months; the Belarusian and Russian militaries have long been integrated. There is no way Belarus could enter NATO under these conditions. And Ukraine includes Crimea and a segment of its territory in the East that is under Russian military occupation. These are the practical difficulties with which expanding NATO in Eastern Europe collides.
In a different sense, the alliance already has 30 members. It has a massive, jagged and unstable eastern border. With each new addition come new military commitments, and the alliance will face serious challenges in the future defending those countries that are already members.
Setting limits can be painful. It entails saying no to partners and friends. It carries its own risks. But it is time for NATO to limit itself -- not for Russia's sake but for the sake of its own coherence and for its own capacities of self-defense.
WHAT MATTERS: You wrote in The New Republic that Ukraine matters as precedent and that Russia should not be allowed to invade or partition a European state. Why is today's situation different than when Russia annexed Crimea from Ukraine in 2014 or parts of Georgia in 2008?
KIMMAGE: This is a difficult question. One might add to it the quasi-annexation of Belarus that Russia has conducted in the past year. That too is a problem. I think the key point here is that both Georgia after 2008 and Ukraine after 2014 retained their basic sovereignty, damaged as it was by Russia's annexation of territory. And of course neither Georgia nor Ukraine is an ally of the US or of NATO, which makes military action only a remote policy option, if it's an option at all.
There are two concerns going forward that may change the equation. One is salami slicing on Russia's part. How many borders can Moscow change before they simply begin redrawing the map of Europe, and that is certainly one worry about a wider war in Ukraine. If left unopposed, even the annexation of a small bit of territory in Ukraine would be leading in a dangerous direction.
But the other concern is more dramatic: Should Russia invade Ukraine with the full force it has gathered on Ukraine's border it might well topple the government and/or partition a substantial part of the country. Instead of eating away at Ukrainian sovereignty, it would be abolishing Ukrainian sovereignty. And a Europe in which borders and sovereignty are effectively poker chips on a big table, which a few players can rearrange at will, is the Europe of the 1920s and 1930s -- an unstable playground of great powers in which nobody is safe, nobody secure and in which nothing is certain.
WHAT MATTERS: Putin's approach to diplomacy, you have noted, has changed over the past year. What's new and what caused the change?
KIMMAGE: Putin's diplomatic style is newly aggressive, newly confrontational and newly rushed. He is issuing ultimatums, behaving rudely and acting as if he needs to get answers immediately, which is unusual for diplomacy in general and for Russian diplomacy in particular. I can only speculate about the reasons for this.
It is one part frustration: Putin feels that since 1991 Russia has been lectured to and dictated to by the West -- that NATO expansion has been a solo act on the part of Washington, DC, which believes it has the power and the right to call the shots not just in Western Europe (which would be OK) but on Russia's doorstep, in Ukraine and elsewhere (which for Putin is not OK). Putin harbors grievances and resentments toward the West and is using this crisis to express them.
It is one part self-confidence or hubris: Putin commands immense military power and has shown that he is willing to use it (in Ukraine, in Georgia, in Syria, etc.). He believes, not without reason, that this degree of military power gives him leverage. And he also thinks that there is a disparity between the leverage he has (in Ukraine and elsewhere) and the degree of respect he is shown by the West.
Another aspect of his self-confidence is his relationship with China, which he did not have in 2014 and which may encourage him to think that he can withstand and overcome Western resistance or Western pressure. He also judges his incursion into Syria in 2015 as a success and may think that in foreign policy, he's on a roll.
It is also one part a low opinion of the West that is driving his behavior: He claims to believe that the West is in decline, that it is not what it used to be, that American foreign policy in particular is a record of overreach and failure (Iraq, Afghanistan, etc.), that the United States is internally divided and less committed to European security than it says it is -- and that Europe as such, whether the European Union or the individual European states, is weak, lacking in organized military power and deathly afraid of military conflict, such that the threat of this conflict may succeed in garnering concessions for Russia.
More than his Western counterparts, Putin thinks that the world has changed in the last 10 years or so, to Russia's benefit and to the detriment of the West. In a sense, the tables are turning.
WHAT MATTERS: President Joe Biden has promised that US troops will not become directly involved in a Russia-Ukraine war. Does the US have enough leverage to keep Russia out of Ukraine?
KIMMAGE: No. What would change the dynamic would be the provision of air power and of US troops to Ukraine. That could stop Putin. The threat of economic sanctions is something that Putin has to take very seriously, but he must have anticipated this before his military buildup.
And the diplomatic leverage that the US has, the leverage that might keep Russia out of Ukraine, entails giving in to Russia, which is absolutely not what Biden wants to do or what Biden will do.
If Putin does not widen the war in Ukraine, it will be because he never intended to do so in the first place; because he sees some cracks in the edifice of the transatlantic relationship; or because he can start getting concessions from the Ukrainian government.
With the exception of keeping up transatlantic unity, which the Biden administration has shown that it knows how to do, the US is not the decisive factor here. The decisive factor is the cost-benefit analysis that Putin will bring to his decision to invade or not to invade. The ball is truly in his court -- for the time being.
WHAT MATTERS: What would you say to everyday Americans about why Russia and Ukraine matter to them?
KIMMAGE: Ukraine and Russia, in the winter of 2022, matter immensely to Americans. Neither country is a big economic factor for the United States. That is not the source of their relevance.
Ukraine matters for what it is: a large country territorially with some 40 million citizens -- and a country to which the United States has, since 2014, made many commitments. The success of Ukraine will be Europe's success.
And the evisceration of Ukraine, on the battlefield, would lead to a Europe defined more by war than by peace. Throughout the 20th century, the US made many sacrifices on behalf of peace in Europe. That's now something that hangs in the balance.
Russia matters for what it is: after the United States, the world's major nuclear power; a linchpin of international politics; a country with Europe's largest conventional army; and a country with the power to wreak immense harm on the United States and its allies.
It is no longer the Cold War. Not everything hinges on the relationship between Moscow and Washington. But even so, this relationship is fundamental to what happens in Europe, what happens in Asia, what happens in the Middle East.
The United States has to be aware of the challenges and threats Putin's Russia poses, and at the same time -- no easy task -- the United States needs to preserve lines of communication with Russia, needs to engage in careful diplomacy with Russia, needs to find a way of dealing with a country that because of its nuclear arsenal cannot be defeated and with a country whose population is not hostile to the United States.
Ukraine and Russia are two separate balls. They're hard to juggle at the same time, but juggle them the Biden administration must. There is no big margin of error.