In the immediate aftermath of a stormy Sunday in the seas off Crimea, it felt that Russia had taken a big gamble and lost.

Whatever local military advantage they may have gained from a direct confrontation with Ukraine, the immediate consequences were surely bigger. There would be more sanctions, serious ones, and further strain on the economy and the rouble.

But the decision by President Poroshenko’s administration to propose martial law seemed to play into the Kremlin’s hands.

Russia disputes Ukraine’s version of events: that three of its boats were attacked, fired on and seized without reason as they attempted to access Ukrainian-controlled ports in the Azov Sea. Russia insists that the route of the three Ukrainian vessels was a provocation, and that they had encroached on its maritime territory.

But there were obvious issues with the Russian account. First, the Azov Sea and Kerch Strait are, according to a 2003 treaty, shared waters, with free navigation guaranteed to both Ukrainian and Russian ships. Second, the distress signal received from the Ukrainian boat was approximately 1km outside of Russian national waters. And, third, a similar group of Ukrainian vessels completed the same trip just a month ago.

Recordings of interchanges between Russian and Ukrainian navy servicemen, released by Ukrainian media, suggest anything but an orderly interception. In one, a Ukrainian officer is heard desperately radioing an SOS for help. In another, what appear to be Russian officers are heard threatening to shoot to kill and demanding the Ukrainian crew appear on deck with their hands up.

Russia and Ukraine have been in de facto conflict since at least 2014 – through the aftermath of the Maidan revolution, the toppling of pro-Moscow President Viktor Yanukovych, the annexation of Crimea, and a four year war in the east that has cost upwards of 10,300 lives.

But this is the first instance where Russia has admitted firing on Ukrainian military objects.

The flashpoint around the Azov Sea, located to the east of Crimea, is itself relatively new. It dates from 2016, around the time Russia began building a bridge between annexed Crimea and the Russian mainland. The Azov Sea is significant for Ukraine in that two important industrial ports are located on the shoreline to the east of Crimea and still controlled by Kiev. Access to it is via the Kerch Straight, now intersected by the bridge.

Tensions have been building for several months, with Ukraine complaining that Russian border guards have been harassing its commercial boats in an attempt to impose a de facto economic blockade. As of today that blockade is a fully declared one, with Russia having parked a tanker across the one open part of the Kerch Bridge for “security” reasons. It is unclear when, if ever, shipping lanes will be reopened.

The Russian seizure of three ships is a severe blow to Ukraine’s navy, and represents about a quarter of its fleet. Little is known of the fate of the 23 servicemen involved, or the six men reported injured (three, according to Russia). But the circumstances in some sense are a replay of the events in Crimea in 2014, during which Russia took over several vessels.

There are several reasons why Russia may have decided to act now but didn’t a month ago.

First are the major anniversaries of the 2013-14 Maidan revolution and 1932-33 Holodomor famine, when millions of Ukrainians died from a starvation attributed to the Soviet leadership. The publicity from these may have been an irritant. Second, western statements of support and promises of military reinforcement may have encouraged the Kremlin to revert to a traditional policy – making opponents think twice before engaging further. Third, a worrying decline in the president’s rating may have encouraged his administration to reintroduce the Ukrainian bogeyman.

Another theory that has been presented by Ukraine-supporting publicists in the west was that this is an attempt to undermine Petro Poroshenko’s administration and create instability ahead of the presidential elections in March.

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That version seems flawed. If the military turn does one thing it is to embolden the Poroshenko administration, which has been flagging in the polls far behind the frontrunner, former prime minister Yulia Tymoshenko. The threat from Russia is a key part of Poroshenko’s three-prong election offer, plastered on posters across the country: Army, Language, Faith.

It does not take a very cynical mind to connect the president’s difficult electoral situation to the proposal to introduce martial law.

No martial law was introduced after the much more violent events of 2014 and 2015. Then the possible damage to the Ukrainian economy and cooperation with the International Monetary Fund put the breaks on such a development. Ukraine has argued that this time things are different, with Russia openly admitting to military engagement. That seems a sophistic argument.

During a short address in his security council, Poroshenko said the imposition of martial law would be limited to 60 days and would not affect civil liberties. In other words, presidential elections might not be postponed as many had feared, but political rallies may be banned in the meantime.

Much of the damage has already been done. On the one hand, Moscow will be delighted by the renewal of its narrative of a “junta” being in charge in Kiev. On another, Ukrainians will wake up to the clear probability of a military tool being used for short-term electoral advantage.