The Ukrainian crisis was never quite forgotten; it has now escalated to an awesome degree and the world is alarmed at the latest bout of Russian expansionism.

The skirmish in the Sea of Azov has bolstered Vladimir Putin’s position at home post the misadventures such as in Syria, not to forget the electoral meddling in the US and the Skripal poisoning in Salisbury. At home, his ratings have slumped sharply because of pension reforms that raised the retirement age. The skirmish in the sea has reaffirmed what has been described as a “masterclass in despotism”.

Last Sunday’s maritime clash in the Kerch strait in Crimea has been an ominous development, and there is little doubt that the Kremlin is trying to extend its control over the former satellites. On closer reflection, there is a geopolitical pattern in this week’s developments.

Russia has been attempting to destabilise Ukraine and consolidate its control of Crimea ever since it was illegally annexed in 2014 after Ukraine’s prowestern protests. It has increasingly flexed its muscle at sea, particularly since the Kerch strait bridge, connecting the Russian mainland to Crimea, was opened in May.

By any reckoning, this is the most serious development since 2014, and the first time that the Kremlin has admitted to the use of force against Ukraine. Notably, the Russian navy has been mobilised and there are no Russian proxies or “volunteers” involved. The sea waves have turned frightfully volatile. Low-level fighting persists in the Donbass region of eastern Ukraine; no fewer than 10,000 people, including 3,000 civilians, have died since hostilities began in 2014. The danger of miscalculations in the Sea of Azov might ignite a more serious conflagration.

Ukraine says the ships were travelling in shared waters, as defined in a bilateral treaty, and that it had notified Russia in advance. Russia has predictably accused Kiev of a “provocation”. Moscow has been seeking to restrict Ukrainian access. In the context of Russia, a Western response may be less than adequate. Very recently, Donald Trump blamed Barack Obama’s “regime” rather than Mr Putin for Crimea’s annexation.

The response of the White House to the latest escalation suggests that the administration might be awaiting the President’s concurrence before coordinating with other nations. Mr Trump has left it to his staff to respond. “Too busy,” was his contrived excuse on Twitter.

The European Union will consider next month whether to impose additional sanctions on Russia, which has in recent times reinforced the raison d’etre for an economic reprisal. Since the annexation of Crimea, pro-Moscow rebels have shot down ~ with a Russian missile ~ flight MH17, killing 298 people. The need for Western solidarity is direly imperative.

Yet this is more easily emphasised than accomplished. The turmoil in the Sea of Azov comes about in the context of a Europe preoccupied by Brexit and, above all, a US President who is expressedly sympathetic towards President Putin. The certitudes of international law lie rather thin on the ground.