In my neck of the intellectual woods, views on the causes of Russia’s recent aggression in Ukraine split into two camps, which I’ll call the Realists and the Russianists. Some people straddle the two groups, and there are other streams of thought on this issue, but mostly the conversation seems to break into competing claims along the following lines.

For their part, the Realists explain Russia’s behavior as a product of the insecurity endemic to the international system. Realism sees world politics as fundamentally anarchic, and the absence of a trusted protector encourages states to husband and grow their power as the only reliable means of protecting their survival and autonomy. This insecurity is so compelling that it even tempts states into expansionist actions aimed at preempting future threats, either directly by winning control over the menacing rival or indirectly by increasing their own power. As Arthur Eckstein (2006, p. 21) describes,

In an anarchic state-system where relations are strongly competitive and conflictual, where unresolved disputes, tensions, and frictions accumulate, and where every state must look primarily to its own resources in order to defend itself, it makes sense for every state to take the strongest possible measures to increase its own security. But measures successfully taken to increase one state’s security act simultaneously to undermine the security of every other state. The result is that the level of tension and distrust intensifies all around. Moreover, making a competitor (i.e., a potential adversary) more insecure not only tends to increase the other state’s interest in militarization but also—as Realists judge from conditions in the modern world—the other state’s own interest in territorial expansion.

Seen through this lens, the revolution in Ukraine in February created both a threat and an opportunity for Moscow. After Yanukovich fled his post, Russia was especially eager to secure control over Crimea because it is home to the Black Sea Fleet, but Putin’s government was also motivated to grab at parts of Ukraine by the continuing expansion of a rival power that already abuts its borders. For Realists, it is not coincidental that Russia’s most aggressive gambits in the past decade have come in Georgia and Ukraine, two countries that border Russia and to which NATO and the E.U. have continued to dangle the promise of eventual membership. Nor is it surprising that Russia seized a chunk of Ukraine and continues to destabilize the rest of it when it looked like Kiev was finally poised to take a clear step toward “the West” by signing an E.U. association agreement and rejecting membership in Moscow’s rival project, the Eurasian Customs Union.

So that’s where the Realists seem to be coming from. The Russianists, meanwhile, see Moscow’s aggression in Ukraine almost entirely as the product of a domestic turn toward chauvinism—or, for the more fatalistic, the resurgence of a chauvinism that never really goes away. Some Russianists see the Putin administration’s waxing nationalism as an earnest manifestation of its core values, while others view it more cynically as a ploy to rally domestic support for the government in the face of a sputtering economy and frustration with authoritarian rule. In either case, though, the root cause of Russian aggression is said to lie within its own borders, and NATO and the E.U. are potential partners whom Russia is rebuffing because its own pathologies blind it to the mutual gains that more cooperative relations would produce.

As is often the case, these competing explanations also imply different expectations about the future. Many of the Russianists I follow have reacted to the annexation of Crimea with predictions that a Kremlin crazy (like a fox?) with nationalism will not stop until it is compelled to stop. They now expect the eventual annexation of eastern and possibly southern Ukraine and see Moldova’s Transdniestr region as a probable next target. Some even warn that the presence of large numbers of co-ethnics in Estonia and Latvia will compel Russia to venture there, and they fear that those countries’ NATO membership, and the untested promise of collective defense it represents, will not suffice to deter this ambition. In their view, the logic of Russian domestic politics now dictates an expansionist line that can only be broken by crippling punishment and loud threats of harsh retaliation.

By contrast, many of the Realists seem less alarmed about where this crisis goes from here. They believe that the same insecurity which motivated Moscow’s recent aggression will also discourage Putin & co. from pushing much farther against the interests of a powerful rival, especially when Russia’s own hard-power resources are already stretched thin and maybe even shrinking. Instead, they expect Moscow to focus on consolidating its recent gains and to avoid provoking an even costlier response by probing the boundaries of NATO’s resolve.

Whether Moscow holds the current line or moves to annex more territory won’t prove one camp right and the other wrong. A single episode will rarely suffice for that, and either course is at least possible under either framework. What it will do, however, is provide new information on which we can and should update our thinking about which view is more right. If Russia stops at Crimea, it would undercut many Russianists’ claims that Putin & co. are compelled by their chauvinist project to “protect” ethnic kin and to continue regrowing the empire. If Moscow does pushes much further, however—and, especially, if it ventures into the Baltic states—it would be hard to sustain the Realist line that domestic nationalism is largely ephemeral to this process.

Importantly, there’s also a prescriptive side to this debate. If the Russianists are (more) right, then now is the Munich moment, and the only way to halt Moscow’s expansionist drive is to make clear to the Putin government that it will suffer badly for its transgressions. If the Realists are (more) right, however, then the bellicose response some Russianists seek could exacerbate the situation by amplifying the security dilemma that underlies the current crisis.

For what it’s worth, my views on this particular case hew closer to the Realists. Russian domestic politics is surely influencing Moscow’s behavior—how could it not?—but if I had to pick a single class of events to which this episode belongs, I would put it in the bin with the many, many other instances of aggressive self-help in response to the insecurity endemic to an anarchic international system. Observers of world politics have noted this pattern for literally thousands of years. Meanwhile, the nationalist turn we’re seeing in Russian domestic politics could be as much consequence as cause of these international tensions, and the idea of Russia as pathologically expansionist is hard to square with the limited scope of Russian irridentism we’ve actually seen over the past 20 years. Europe and the United States may insist and genuinely believe that they mean Russia no harm, but their active and vocal pursuit of democratic change in Moscow undercuts this claim, at least in the eyes of the people who staff the apparatus that actually makes Russian foreign policy. That pattern doesn’t justify Russian aggression, but I do think it goes a longer way toward explaining it.