Russia’s deployment of S-400 surface-to-air missile systems in Crimea, announced on Wednesday, sounds worrying. The move comes days after Russian forces fired on Ukraine’s navy in the Kerch strait, prompting western condemnation and fears of a wider conflagration. At first glance, Vladimir Putin appears to have opted for defiance and escalation.

But first glances can be misleading. All parties to the Crimea-Donbass conflict have an interest in shaping outside perceptions, and not all is what it seems. In fact, Russia has stationed three S-400 missile battalions in Crimea since 2014, when it seized and illegally annexed the peninsula. It is now adding a fourth. It is not welcome news, but it is not necessarily a prelude to all-out war.

Opinions differ about the Russian president’s motives. Western analysts suggest he is intent on blockading the Azov Sea and eastern Ukraine’s industrial ports, thereby weakening Kiev economically and demonstrating Moscow’s superior control. Russia could also be reacting to Ukraine’s plan to build a new Azov naval base. This in turn may all be part of a long-term strategy to push Nato out of the Black Sea region.

On the other hand, Putin’s domestic approval ratings are falling, hit by a row over pensions and economic problems caused by western sanctions. When Putin ordered the Crimea invasion, his popularity surged to 80%, compared with 30% the year before. Maybe he is trying to pull the same trick again. If so, it’s a dangerous game.

The motives of Petro Poroshenko are likewise open to question. Ukraine’s president warned this week of “full-scale war”, claiming to have detected a recent buildup of Russian tanks at the border. In fact, Russia started relocating army units closer to Ukraine four years ago. This led over time to a “substantial expansion of Russia’s military presence”, according to Harvard’s Belfer Center. But it’s not new.

Is Poroshenko deliberately exaggerating the imminence of the Russian threat? He faces elections in March that he is tipped to lose. Opponents suggest his emphasis on Ukraine’s endangered security, and imposition of martial law, could compromise the democratic process. Sergii Leshchenko, an opposition MP, said Poroshenko’s re-election hopes rested on a nationalist tripod: “Language, faith, army.”

Western motives are also suspect. Pentagon hawks have an interest in stiffening Donald Trump’s support for Nato in general and Ukraine (an aspiring Nato member) in particular. The Kerch confrontation highlights Putin’s repeat offending, as they see it, in eastern Europe, the Baltic, the Balkans, Syria and Salisbury. The crisis could be used to draw the US and Europe closer together at a time of transatlantic rifts – and strengthen the case for western arms sales to Ukraine, even for direct intervention.

Trump is now under pressure to cancel his G20 meeting with Putin this weekend. In Washington, this is all mixed up with the FBI investigation into Trump’s past dealings with Russia and current appeasement of Putin. Reflecting these sensitivities, the White House has mostly steered clear of the Kerch row. The US so far has not responded substantively to European calls for new sanctions or Kiev’s pleas for help.

If Putin hoped to expose western divisions and exploit Trump’s ambivalence, he has succeeded. If Poroshenko, by launching what Moscow calls a provocation, wanted to boost his political fortunes, he may have succeeded too. Or maybe it is less complicated. Maybe excitable mid-level Russian commanders simply exceeded their authority. That’s believable. And that’s how wars start.