In response, Ukraine’s president, Volodymyr Zelenskiy, has been engaged in an intense bout of diplomatic activity, calling for the west to strengthen its presence in the region – and pressing for a pathway to join Nato, the membership action plan, which the alliance has yet to grant despite promising to do so as long ago as 2008.
Turkey said over the weekend that two US destroyers were expected to enter the Black Sea, although they would be no match for the Russian fleet, with 45 vessels. The UK, which signed a military cooperation agreement with Ukraine last October, flies spy planes in the region to monitor troop movements.
Potentially more significant, however, was Zelenskiy’s visit to the Turkish capital, Ankara, where he met his Turkish counterpart, Recep Tayyip Erdoğan, for three hours of talks on Saturday to discuss defence industrial cooperation.
Reports circulated afterwards that Ukraine would buy next-generation Turkish Bayraktar drones on top of at least six it owns already. Such weapons proved devastatingly effective when used by Azerbaijan against Armenia’s Russian-made tanks in Nagorno-Karabakh last autumn.
Few believe that immediate military action is likely. Security at the Voronezh staging post was sufficiently lax that journalists from Sky News were able to drive in, and if an attack was seriously meant then it would be more likely be conducted by surprise, according to Maryna Vorotnyuk, a research fellow at the Rusi thinktank.
She argued there were several reasons why Russia would want to raise tensions. Relations with the US are poor after Joe Biden agreed that he thought Vladimir Putin was “a killer” in a TV interview last month, prompting Moscow to recall its ambassador.
It could help in “distracting the attention from [Alexei] Navalny”, the dissident whose health is deteriorating rapidly in jail, she added, and could be a response to Zelenskiy’s hardening stance on Russia, with Kyiv having targeted the oligarch Viktor Medvedchuk – the main Russian ally in Ukraine – with sanctions.
“These are classical tools from the Russian military playbook: sowing confusion about Russian real intentions and limits,” Vorotnyuk added.
But there remains a fear that the Kremlin could be looking for a pretext to go further, forcing Kyiv into actions that Moscow could then seek to exploit.
Last week Dmitry Kozak, Putin’s deputy chief of staff, said Moscow could “come to the defence” of Russian-backed separatist territories, and warned of potential ethnic cleansing in the Donbas, although there is no evidence that this is taking place.
Nigel Gould-Davies, a Russian specialist with the IISS thinktank, said: “We should be prepared for surprises. Any threat to Ukraine is by extension a challenge to Europe. It is a situation that will be a test of European and transatlantic resolve.”