Kyiv's parliament approves martial law after the Kerch Strait clash
A retrospective on the Verkhovna Rada vote of 26 November 2018, a day after Russian forces fired on and seized Ukrainian naval vessels.

What did Ukraine's parliament decide a day after the confrontation in the Kerch Strait? On 26 November 2018, the Verkhovna Rada approved the introduction of martial law in 10 oblasts for a period of 30 days, to take effect from 28 November 2018.
The incident behind the vote
The decision followed events on 25 November 2018 near the Kerch Strait. As reported at the time, a Russian border patrol ship, the Don, rammed the Ukrainian naval tug Yani Kapu while a group of Ukrainian Navy boats was moving from Odesa to Mariupol. The Russian side then opened fire on the group. Three Ukrainian vessels were seized, and 23 sailors were taken prisoner, six of them wounded.
In later accounts, the incident is described as one in which Russia's Federal Security Service coast guard fired on and captured the three Ukrainian Navy vessels as they tried to pass from the Black Sea into the Sea of Azov on their way to Mariupol. The same account describes it as the first time Russian forces had openly engaged Ukrainian forces during the Russo-Ukrainian War.
What parliament approved
The Rada's vote came explicitly in response to the actions of Russian border ships against Ukrainian Navy vessels in the strait. The measure covered 10 oblasts rather than the whole country, and it was limited to 30 days, with the start set for 28 November 2018, two days after the vote.
The sequence was swift: the clash on 25 November, the parliamentary approval on 26 November, and the start of martial law on 28 November 2018. The vote made the Kerch Strait confrontation a matter of national emergency legislation in Kyiv within a single day of the capture of the ships and crews.