A flare-up of military hostilities between Russia and Ukraine—in the form of a Russian-instigated naval skirmish in the Sea of Azov over the weekend—has left Western capitals scrambling to formulate a robust response. Truth be told, however, Russia’s renewed aggression should not have come as a surprise. Rather, as officials in Kyiv have consistently warned, an intensification of the on-again, off-again shooting war between the two countries was only a matter of time, for five main reasons.

The military imbalance between Russia and Ukraine is significant—and growing. True, Russia’s 2014 invasion of Ukraine had the unintended consequence of galvanizing Ukrainian nationalism and spurring a massive recapitalization of the Ukrainian armed forces, with significant results. Ukraine now boasts the second-largest standing army in Europe (after that of Russia itself), and one that—thanks to NATO and U.S. assistance—is increasingly professional and capable.

Even so, Russia’s growing military modernization is steadily expanding the Kremlin’s strategic capabilities, and doing so at a pace with which Ukraine cannot compete. Earlier this year, Gen. Curtis Scaparrotti, the head of U.S. European Command, warned that the Kremlin’s defense investments have become so significant that Russia could be in a position to challenge American military superiority in Europe by the middle of the next decade. Against this backdrop, Ukraine’s gains—however impressive—are simply being eclipsed by those of Russia.

Ukraine’s navy is still provocatively weak. The military mismatch between the two countries is particularly glaring in the maritime arena. The 2014 Russian annexation of the Crimean Peninsula, following a political referendum stage-managed by Moscow, proved to be ruinous for Ukraine’s naval capabilities. During the course of that takeover, Russian forces seized an estimated 70 percent of the Ukrainian Navy’s military hardware, ousted the service from its longstanding headquarters in Sevastopol, and prompted three-quarters of Ukrainian naval personnel to either defect outright or abandon their posts. And while Ukraine’s military standing has improved overall since then, Kyiv’s maritime capabilities have continued to lag behind the times. Last summer, Ukrainian military officials visiting Washington warned starkly that the country still lacked an independent maritime force capable of countering Russian aggression.

More than a year on, not all that much has changed. Despite efforts at reform and reorganization, the naval component of Ukraine’s armed forces continues to trail the rest of the Ukrainian military in terms of both capability and resources. And because it does, it represents an inviting target for a Russia that continues to seek to assert its military dominance.

The Kremlin is once again attempting to change the political conversation. The old adage posits that “all politics are local,” and Russia’s escalation of hostilities could have distinctly domestic roots. Alina Polyakova of the Brookings Institution has pointed to recent internal polling which highlights a marked decline in Russian president Vladimir Putin’s approval ratings. This, she suggests, could mean that the Kremlin’s renewed foreign policy adventurism represents an effort to distract from the country’s mounting internal malaise.

Admittedly, accurate barometers of domestic sentiment within Russia are notoriously unreliable—something that even Russians themselves acknowledge. More than half of respondents in a recent poll carried out by the Moscow-based Russia Public Opinion Research Center (VTsIOM) said they believe that polling results in Russia are “fabricated” and published in order to manipulate public opinion.

Even so, it is a theory worth considering. After all, Russia’s decision to intervene militarily in Syria in September 2015 was driven in no small measure by the fact that its then year-and-a-half old campaign in Ukraine was going far more poorly than the Kremlin had anticipated—or was prepared to admit. The same sort of effort to distract may have factored into Russia’s decision to intensify its aggression against Ukraine now.

Russia is trying to expand its leverage over Ukraine—and Europe. Since the start of the current round of Russo-Ukrainian hostilities in 2014, the Kremlin has consistently sought to undermine Ukraine’s sovereignty as part of its ongoing “hybrid war.” It has done so, most directly, through staffing, training, equipping and leading separatist forces in Ukraine’s east. But Russia’s efforts at destabilization possess a distinct economic component as well; by stoking separatism in Ukraine’s Donbas region, which provided nearly one-fifth of Ukraine’s pre-war GDP, the Kremlin has sought to weaken the country’s overall economic stability.

The latest Russian aggression follows the same logic. For months, Russia has been harassing commercial vessels in the Black Sea, causing jitters in Western capitals in the process. This weekend’s temporary blockade of the Sea of Azov and direct attack on Ukrainian naval vessels is an escalation of the same pattern—one intended to send a clear message to foreign countries and companies that doing business with Kyiv remains a risky proposition.

That, in turn, reflects what is perhaps the most fundamental problem of all: Russia simply isn’t sufficiently deterred at present. Recent years have seen escalating American assistance to Ukraine, and a growing NATO operational tempo in the Black Sea region. Yet, despite these developments, the Kremlin clearly still has serious doubts about the will of Western nations to resolutely respond to its military adventurism.

All of which makes the U.S. and European response to the current crisis a crucial test of collective credibility. Should Washington and its European partners fail, it will virtually guarantee more of the same from Moscow in the future.

Ilan Berman is Senior Vice President at the American Foreign Policy Council in Washington, DC.

Image: A member of the Ukrainian State Border Guard Service stands guard at the Goptovka crossing point on the border between Russia and Ukraine in Kharkiv Region, Ukraine November 28, 2018. REUTERS/Vyacheslav Madiyevsky​.