Seized Ukrainian military vessels are seen in a port of Kerch, Crimea, on Nov. 26, 2018. (STR/AFP/Getty Images)

The Nov. 25 skirmish between Russian Border Guard and Ukrainian navy ships in the Kerch Strait has escalated tensions not just between the two countries, but also between Russia and NATO.

Two Ukrainian navy small-armored boats and a tugboat attempted to cross into the Sea of Azov via the Kerch Strait. A Russian Border Guard ship rammed the tug. Russian forces eventually captured all three boats, holding them in the Crimean port of Kerch. 

This crisis kicked off months ago 

In March 2018 Ukraine seized a Russian-flagged fishing vessel, claiming that it had violated exit procedures from the “temporarily occupied territory of Ukraine.” Although the Russian crew was released, the boat remains detained in a Ukrainian port. Subsequently, Russia began to seize Ukrainian vessels for inspection, starting in May when a fishing vessel was detained for illegally fishing in Russia’s exclusive economic zone.

A new Russian-built bridge linking Crimea to southern Russia is at the center of Russia’s attempt to assert sovereignty over the entire Kerch Strait. The bridge opened in May, and its low clearance height cut off many commercial ships and reduced revenue at the Mariupol port by 30 percent. Russia has imposed an informal blockade on the remaining maritime traffic, with ships often waiting more than 50 hours to cross, and Russian authorities insisting upon inspecting the cargo. This has substantially raised transit costs — and has been slowly strangling the Ukrainian ports of Mariupol and Berdyansk.

So, what just happened? 

Russia transferred several naval ships over the summer from the Caspian Sea to the Sea of Azov as a prelude to setting up a separate flotilla there. In recent weeks, tensions have gradually increased, with Russian officials repeatedly claiming that its maritime inspection regime is lawful and does not violate any existing international agreements.

Last week’s encounter was Ukraine’s first attempt to bring armed naval ships through the Kerch Strait since the completion of the bridge. Previously, armed Ukrainian naval vessels had entered the Sea of Azov through internal waterways.

According to the Russian FSB’s narrative of events during the confrontation, the Ukrainian ships gave the Russian authorities advance notice of their intent to travel through the strait, but were informed the strait was closed and that they had failed to give sufficient advance notice.

From the Russian point of view, the Ukrainians knew the procedure for innocent passage into the Sea of Azov and did not go through the proper channels to receive a place in line to cross the strait. The Ukrainian position is that their notification of intent to cross into the Sea of Azov was sufficient and that there was no international notice regarding closure of the strait to maritime traffic.

A skirmish at sea

The naval battle was brief. The Russians gave the Ukrainian ships the order to halt, and when they refused to comply, a series of dangerous maneuvers culminated with the Don patrol ship ramming the Ukrainian navy tug. Subsequently Russia called in air power reinforcements, with two Ka-52 helicopters and two Su-25 ground attack aircraft, along with several other ships. It also blocked the channel under the bridge with a tanker. Later that evening, Russian ships pursued the Ukrainian vessels and a brief gunfight left six wounded before the Russians captured the three Ukrainian ships.

According to Ukrainian accounts, the Russian Border Guard vessel fired directly at one of the Ukrainian ships, while the Russian account claims that direct fire was initiated only after an initial round of warning shots was ignored. The Ukrainian account claims the ships were captured outside the 12-mile zone of Russian territorial waters, while the Russian side argues that the ships were still within Russia’s maritime boundary. 

Assessing the damage — and potential benefits

Based on these accounts, it seems clear that Russia violated the terms of the 2003 bilateral treaty on the status of the Sea of Azov, since Russia adopted rules on advance notification of passage through the Kerch Strait in 2015 unilaterally, following the annexation of Crimea. There was no Ukrainian agreement on the new rules. The treaty itself clearly states that warships belonging to both countries have freedom of navigation through the strait and does not specify any notification procedures for such ships.

In the past, Ukrainian ships have notified Russian authorities about their passage through the strait to ensure the safety of navigation through a relatively narrow and often congested passage. Because Ukraine does not accept Russian sovereignty over Crimea, Ukrainian authorities have refused to accept any suggestion that their ships would need Russian permission to transit the strait. From the Russian point of view, this situation is a violation of its territorial sovereignty and an affront to its power in the region.

For Russia, the quick victory is a reminder of its military dominance in the region, particularly in the maritime domain. Russian leaders probably determined that the potential costs would be small, limited to statements of condemnation by hostile Western powers and perhaps some minor additional sanctions. NATO called for “restraint and de-escalation,” and for “Russia to ensure unhindered access to Ukrainian ports in the Azov Sea.”

Ukraine seeks to contest the emerging status quo, where post-annexation Russia controls access to the Sea of Azov in practice. It also seeks further Western support and military aid, so Russian aggression helps make the case with supportive audiences. Ukraine’s leadership is trying to leverage the confrontation as a way of rallying the population. Elections are coming up in 2019 and the Ukrainian government and President Petro Poroshenko are highly unpopular. Poroshenko’s quick move to capitalize on the situation by seeking to introduce martial law has fed speculation along these lines.

During the events on Sunday, Ukraine sought to demonstrate that Russia is not the master of the Sea of Azov, while Russia sought to communicate that it indeed was. Readers can judge for themselves the outcome. It is unlikely that this confrontation will lead to a broader conflict between Russia and Ukraine, as such a conflict is not in either side’s interest at the present time.

Will Russia use the skirmish as a pretext to block all Ukrainian military transit through the Kerch Strait? Regardless, neither side is likely to back down from its position on the Sea of Azov and passage through the Kerch Strait, so tensions will remain high and additional skirmishes in the coming months cannot be ruled out.

Dmitry Gorenburg is a senior research scientist in the strategic studies division of CNA and an associate of the Davis Center for Russian and Eurasian Studies at Harvard University.

Michael Kofman is a senior research scientist at CNA and a fellow at the Wilson Center, Kennan Institute.