Editor's note: On Thursday, President Trump said on Twitter he had canceled a planned meeting with Russian President Vladimir Putin, citing intensifying Russian aggression toward Ukraine.
In late September, the Ukrainian navy announced that two of its vessels had successfully traveled from the Black Sea to the Sea of Azov, passing through waters controlled by the Russian "aggressor" and exercising Ukraine's maritime rights under international law.
On Sunday, three more Ukrainian vessels attempted to make the same journey. This time, the Russian coast guard intercepted the Ukrainians, ramming a tugboat and firing on the gunboats.
Russian authorities said that unlike before the passage in September, the Ukrainian vessels had failed to request permission and ignored orders to stop. Russia seized the three boats and took the two dozen crew members prisoner, several of whom had been injured in the clash.
Ukraine insisted on its freedom of navigation and said its seamen had become the victims of an unprovoked attack.
It is not by chance that the 4 1/2-year conflict between Ukraine and Russia has taken on a naval dimension. For Kiev, keeping the Sea of Azov open to its ships is more than just a matter of legal principle — it's a strategic and economic imperative. For the Kremlin, the challenge posed by Ukraine's tiny navy is almost entirely symbolic.
While there are real fears in Kiev of all-out war, neither country could afford a serious escalation. Following fierce combat in the first year of the conflict, the Kremlin has largely stuck to prosecuting a low-level war with occasional flare-ups. The naval skirmish over the Sea of Azov is primarily about Russia imposing on Ukraine the irreversibility of its annexation of Crimea.
The Sea of Azov is a shallow body of water that Ukraine shares with Russia. Its only access to the open seas is through the Kerch Strait, which connects it to the Black Sea.
After Russia occupied and seized Crimea from Ukraine in 2014, the Kremlin gained de facto control over both sides of the Kerch bottleneck — even if practically no other country recognized the Russian annexation de jure. In May, Russian President Vladimir Putin personally opened a 12-mile-long bridge over the Kerch Strait. The Crimean Peninsula, which juts into the Black Sea from the Ukrainian mainland, was literally cemented to Russia.
Putin's bridge is a symbol of Russia's claim on Crimea. Since Sunday's skirmish, it has also become the physical gateway to the Sea of Azov. To prevent the three Ukrainian boats from passing under the bridge, Russia placed a cargo ship below it.
Ukraine depends on the port of Mariupol to export grain and steel via the Sea of Azov. After Ukrainian authorities said Russian forces were disrupting shipping in that sea, the government in Kiev announced its intention to build a naval base at the port of Berdyansk.
"Russia's purpose is to occupy the Azov Sea, the same way it did Crimea. This is a brutal violation of international law, and we cannot accept it," Ukrainian President Petro Poroshenko told The Washington Post in September. "We have absolutely clear legal status in the Azov Sea. Russia has no right to attack or stop our vessels."
When the first two Ukrainian naval boats passed under the Kerch bridge to the Sea of Azov that same month, Poroshenko thanked the crews for a "perfectly executed order" and said the two aging vessels would be stationed at the new base. A few days later, Poroshenko traveled to Baltimore to officially receive two U.S. Coast Guard patrol boats that will be delivered to Ukraine next year.
Ukraine is no match for Russia in terms of sea power.
After Ukraine gained independence from Moscow in 1991, most of the Soviet Black Sea Fleet ended up going to Russia. In an agreement that would later prove fateful, Ukraine allowed Russia to use the Crimean port of Sevastopol as the main base for the Russian Black Sea Fleet. When Putin ordered the occupation of Crimea in February 2014, Russian forces with unmarked uniforms and vehicles fanned out across the peninsula from Russian Black Sea Fleet facilities.
Putin justified Russia's takeover as the free choice of Russian-speaking Crimeans who feared Ukrainian nationalists coming to power after street protests in Kiev brought down a Kremlin-backed government. Putin also said he couldn't countenance the presence of "NATO sailors" in Sevastopol should Ukraine one day join the U.S.-led alliance.
Ukraine's navy estimates it lost at least 80 percent of its assets and capabilities after the annexation of Crimea, as its most important bases were located on the peninsula. Russia's seizure of the two gunboats on the weekend is a further blow.
After the clash, Poroshenko called Russia's actions at sea "a new stage of aggression." If Russia's war against Ukraine had previously been clandestine, he said, Sunday's incident was an open attack. Poroshenko warned that new intelligence suggested "an extremely serious threat of a land-based operation against Ukraine" that warranted the imposition of martial law.
Domestic opponents of the unpopular president accused him of planning to use martial law as a way to suspend an election scheduled for March 31. Poroshenko only got Ukraine's boisterous parliament to approve the measure once he had watered down his proposal by reducing martial law — which entered into force Wednesday — to 30 days from 60, limiting it to border regions and promising not to postpone the election.
Sonya Koshkina, the editor of the Kiev news site lb.ua, wrote that Poroshenko's lack of transparency in pushing through martial law had increased "the gap between the government and the Ukrainian people." Ukrainian journalist Maxim Eristavi warned that martial law itself could crush Ukraine's fledgling democracy.
While Putin blamed Poroshenko for a pre-election "provocation" to boost his sagging popularity, the flare-up in tensions doesn't exactly hurt the Russian president domestically either.
After his triumphant re-election to a fourth term in March, Putin's approval ratings have taken a hit amid anger over the government's raising of the retirement age, rising fuel prices and tax hikes. The portion of Russians who say they trust Putin has dropped 20 percentage points to 39 percent within less than a year, according to the independent Levada Center. His popularity was at an all-time high after the annexation of Crimea.
Ukraine's biggest problem in its struggle with its giant neighbor is keeping the world's attention — especially that of the United States.
While the leaders of NATO, the European Union and Germany spoke out against Russia's seizure of the Ukrainian boats and their crews, President Trump left it to his ambassador to the United Nations, Nikki Haley, to condemn the move as an "outrageous violation of sovereign Ukrainian territory."
In a Monday interview with The Washington Post, Trump suggested he may cancel a meeting with Putin planned for later this week as a result of the naval clash.
But in a White House briefing the next day, national security adviser John Bolton made no mention of any cancellation and indicated that Haley had spoken the administration's final word on the Kerch Strait incident.