What did Ukraine's entry ban on Russian men mean?

What did Ukraine do on 30 November 2018 to limit movement from Russia, and why? On that day Ukraine banned Russian men aged between 16 and 60 from entering the country, following the imposition of martial law. President Petro Poroshenko said the ban was meant to prevent the formation of "private armies" in Ukraine. Russia said it did not plan to retaliate.

The backdrop: the Kerch Strait incident

The measures followed the Kerch Strait incident of 25 November 2018, when the Russian Federal Security Service coast guard fired upon and captured three Ukrainian Navy vessels. They had been trying to transit from the Black Sea into the Sea of Azov on their way to the port of Mariupol. It was the first time Russian forces had openly engaged Ukrainian forces during the Russo-Ukrainian War.

A port blockade in all but name

On 29 November 2018, Ukraine's Infrastructure Minister Volodymyr Omelyan said the ports of Berdiansk and Mariupol were effectively under blockade, because Russia was refusing to let any Ukrainian vessels leave or enter the Sea of Azov. The same day, Poroshenko called on NATO to send warships to patrol the Sea of Azov.

Diplomacy at the G20

The crisis also reached the planned meeting between U.S. President Donald Trump and Russian President Vladimir Putin at the G20 summit in Buenos Aires. On 29 November 2018, Kremlin spokesman Dmitry Peskov said the meeting was still on. While flying to Argentina, Trump tweeted that he had decided, after conferring with his top National Security advisers, to cancel it. He said it was not a good time since Russia had not returned the ships and sailors to Ukraine. Less than an hour earlier, he had said he would "probably" meet Putin and believed it was a good time for the meeting.

Signals from NATO's Baltic mission

Elsewhere in the region, the Belgian Air Component said on Twitter on 29 November 2018 that, the day before, its F-16s flying in the Baltic region for NATO's Baltic Air Policing mission had intercepted Russian Flanker jets, allegedly because they had no flight plan.

A domestic footnote

Separately, a decree of Ukraine's Cabinet of Ministers on 28 November 2018 returned the buildings of the Pochaiv Lavra to the Kremenets-Pochaiv Reserve.

Taken together, the reports from 28 to 30 November 2018 show Kyiv tightening border controls at home while seeking support abroad, and the fate of the captured ships and sailors weighing on a planned US–Russia meeting.