On November 25, 2018, Russian warships fired at three Ukrainian vessels in the Black Sea. Ukraine subsequently announced that the three ships and 23 Ukrainian sailors were detained by Russian forces following the attack, while six of the sailors were injured. Russian aggression sparked diplomatic responses from the United States and other countries. These included a decision by President Trump to cancel talks with Russian President Vladimir Putin at the November G20 summit in Argentina. In response to the diplomatic pressure, Russia released an official statement saying that Kiev never notified Moscow that the two gunboats and single tugboat were going to pass through the Kerch Strait. Upon Ukrainian approach, Russian sailors were forced to take action because they were unaware of the ships’ intentions. Verifying this claim is difficult, but even if it is true, Russian actions may not be justified under international law. Furthermore, two other questions remain: What are Russian motives for the aggression, and how if at all, should other actors respond to the situation?

On one side of the Kerch Strait is Russian territory and on the other is territory widely recognized by the international community as Ukrainian. That Ukrainian territory is Crimea, which was an autonomous republic within Ukraine until 2014, when Russian troops occupied the peninsula, claiming it to be under control of the Russian Federation. While the international community at large does not recognize the legitimacy of Russia’s occupation, Russia maintains its stance concerning ownership of the territory. Due to the lack of support for the Russian annexation, one possible set of motives Russia holds is that firing on the vessels was simply a way of trying to display and extend the validity of Russian claims to Crimea. This explanation makes sense given that Crimea’s geopolitical significance to Russia is twofold. First, the Sea of Azov is home to the Ukrainian port of Mariupol. Russia and Ukraine are both woefully lacking in ports that connect to the rest of the global trade network, and as such, Mariupol is one of the linchpins of the Ukrainian economy, which is heavily dependent on exports of raw and manufactured materials. In the event that Russia establishes firm control over Crimea, it is quickly able to close Ukraine off from its main port. Secondly, control of Crimea and the Sea of Azov would provide Russia with a massive tactical advantage in the event of a large-scale armed conflict. As it stands, Russia and Ukraine share one land border where Ukraine could station the majority of its troops.  Hence, in a scenario where Russia establishes maritime primacy in the Sea of Azov, major Ukrainian cities would be attainable for the Russian navy, and Ukrainian troops would have to be diversified throughout the new borders that open up, allowing Russia to surround and defeat the Ukrainian military with relative ease.

However, even in the worst case it is rather safe to assume that a hot war between the two nations is unlikely. Even so, there are likely implications for the two countries in peacetime. In addition to the annexation of Crimea, Russia has implemented a multitude of measures to increase control over the Sea of Azov. In 2015, Moscow began the construction of a bridge over the Kerch Strait that limited the size of shipping vessels and streamlined the transportation of troops and arms into Crimea. Russia has already imposed waits and halts to Ukrainian shipping traveling through the strait, while levying a tax on boats passing through the Kerch Strait. Such intervention in the Ukrainian economy is well in line with a strategy Russia commonly employs called hybrid warfare. Hybrid warfare is the usage of conventional armed forces supplemented by other tactics that are not considered to be conventional force, such as troop deployments, bombing runs, or cruise missiles. The annexation and ensuing control of Crimea for the purpose of putting the Ukrainian economy in a stranglehold is a perfect example of hybrid warfare. They are also in line with past Russian actions in Eastern Europe. For instance, Russia perpetrated cyber attacks against Georgia and provided assistance to local independence militias to take control of administrative buildings in the country, with both tactics culminating in the Russo-Georgian War of 2008. Why would Russia want to maintain economic control over Ukraine? Most likely, Russia fears Ukrainian accession to NATO. Due to Article 5 of the North Atlantic Treaty, which stipulates that an attack on one NATO country is an attack on all of them, it would become inconceivable for a Russian incursion like that against Crimea in 2014 to happen again, and proceedingly, Russia’s imperialistic and mercantilistic foreign policy in the region would experience a significant recession. From the Russian perspective, this problem has a straightforward remedy. Russian control over the goods flowing in and out of Mariupol means that it can eliminate the threat of NATO in the region before it even arrives, since Ukrainian entrance or even a perceived pivot towards NATO would be met with a Russian economic stranglehold that could not possibly be sustainable for Ukrainians.

Russian motives aside, the question still remains as to whether or not Russia was acting within its rights under international law when it fired on the Ukrainian vessels. When deciding who is at fault for the incident, there are two legal documents to consult. One is the United Nations Convention on the Law of the Sea (UNCLOS) and the other is the 2003 Treaty on the Cooperation in the Use of the Sea of Azov and the Kerch Strait signed by both Russia and Ukraine. UNCLOS is an agreement of international customary law that came into force in 1982. Both Ukraine and Russia are signatories to the agreement ‒ with Russia having acceded to it and Ukraine having ratified it ‒ meaning that both parties have agreed to act in accordance with its rules. Given that both parties have given affirmative consent to act under the rules provided by the agreement, what specific rules and stipulations in UNCLOS apply to this case? The applicability of UNCLOS in this situation depends on whether or not the Russian annexation of Crimea in 2014 is legally valid. This is not easy to determine, because while Russian troops still occupy the peninsula, there is little to no international recognition of the annexation of the territory. On the condition that the annexation is considered legal, the two vessels would have been operating in the so-called “territorial waters” of Russia. Under UNCLOS, all nations have the freedom of “innocent passage” through the territorial waters of other nations. This would mean that Russia needs to prove that the actions of the Ukrainian ships were not innocent. The UN law defines passage as innocent “so long as it is not prejudicial to the peace, good order or security of the coastal state.” Despite claims by Russian officials, it would seem to be nearly impossible to prove that Ukrainian ships were acting in a hostile manner, and considering that there were a lack of valuable tactical targets nearby, Ukraine has no obvious incentive to act in such a manner. All that said, if you consider Russia’s annexation of Crimea to be illegitimate, as the majority of nations do, the Ukrainian vessels were operating within their own territorial waters and could not have been legally seized by Russia.

The other sections of UNCLOS that may be relevant when analyzing this incident are Articles 38 and 44. These articles stipulate that states shall not hamper the ability of maritime vessels to travel through straits within their territorial waters. The Ukrainian vessels were on their way through the Kerch Strait, which is bordered on one side by Russia, and on the other side by Crimea. Even in the scenario that the Russian annexation of Crimea is licit, a state such as Russia is obliged, in accordance with UNCLOS, to provide Ukraine passage from one area of high seas to another. High seas are defined by UNCLOS as waters that are not within the territorial waters of any state. The Kerch Strait is the only way in which Ukrainian vessels are able to travel from the section of high sea located in the Black Sea to the section located in the Sea of Azov. As such, the right of Ukrainian vessels to pass through the strait cannot be infringed upon.

While Russian aggression under UNCLOS seems to be unjustified, there is also the 2003 agreement forged between the two nations. The agreement states that the Kerch Strait and the Sea of Azov are the shared internal waters between the two countries. Furthermore, it “affords Russian and Ukrainian merchant vessels, warships, and State ships flying the flag of Russia or Ukraine ‘freedom of navigation’ in the Sea of Azov and in Kerch Strait.” This agreement would take precedence over UNCLOS in this scenario because regardless of the coastline that the two states were operating near, the ships that were captured in an area that both nations have agreed upon is shared territory. By engaging in a past treaty, Moscow and Kiev have laid down their internationally recognized rights to a personal maritime zone off their coastline in this area, which means Russian aggression is decidedly illegal under this agreement as well.

Given the massive implications to the Ukrainian people, what should the response from other countries be? On November 29, Ukrainian President Petro Poroshenko called for NATO warships to visit the region and “provide security” to the waters. However, no such visit has happened, and likely for two reasons. The 2003 Agreement states that any vessels from third parties outside of Ukraine and Russia need to be approved by both governments. Obviously enough, Russia would not approve of the vessels, and as such, NATO would be trying to preserve international law and norms by trampling those same agreements. International law is fragile, especially when one of the parties expected to act in accordance with it is Putin, a devout practitioner of realpolitik. Second, the actual effects of deploying these vessels seem to be dubious. While it is possible that the peacekeepers may be able to secure the region for travel by merchant and shipping vessels, tensions would be high, and the chance for a military miscalculation would be above acceptable levels, as one misstep could result in armed conflict.

If not military action, then what about diplomatic means? The United Nations Security Council could very well approve the deployment of a maritime peacekeeping core, but Russia would be able to veto its deployment. Even if the Security Council could convince Russia not to veto, the same problems attached to the aforementioned NATO solution could still arise. Another option remains in the hands of German Chancellor Angela Merkel. The Russian natural gas pipeline Nord Stream Two would double Russian supplies of gas to Germany, while also bypassing Ukraine. Current pipelines between the two countries travel through Ukraine, which makes a substantial profit from transit fees when Russian natural gas passes through its territory. Conversely, the newly proposed project would circumvent Ukraine and slowly wean Ukraine off the profits it obtains from Russian gas going to Germany. However, as a bipartisan agreement, Merkel has the ability to make German participation in the pipeline contingent on a decrease in Russian aggression in the Kerch Strait and Sea of Azov. This would appear to be the best course of action, because while no one will go to war over a single pipeline, it may very well have the teeth to make Moscow back down.