Something very serious is happening in the Black Sea, and it demands a response. Merchant ships are being attacked and sunk without warning in the latest, highly provocative action in Russia’s shadow war against European NATO members.

A slew of drone attacks on merchant vessels off the coasts of Romania and Bulgaria, attributed to Russia, have killed at least two sailors and left 21 missing. On October 5, a Turkish cargo ship hit by drones sank in Romania’s exclusive economic zone. The following week, two chemical tankers were set ablaze, one just inside and one just outside Romanian territorial waters. A total of seven ships have been hit. Romania responded on October 17 by shooting down two drones identified as jet-powered Russian Geran 4s, which were headed westward toward the country.

Some of the vessels were engaged in trade with Ukraine, but several were not, suggesting that the Kremlin’s attacks served a wider and more worrying purpose.

Bulgaria has now asked NATO for the deployment of combat aircraft and anti-drone systems to its territory. “We have sent letters and a request to the NATO Secretary General and the Supreme Allied Commander, urging them to strengthen our capabilities, which also means deploying additional forces on our territory. We are awaiting their decision,” Defense Minister Dimitar Stoyanov said on October 16. On October 18, France sent a maritime reconnaissance aircraft to Romania.