When negotiators left Abu Dhabi after two days of talks, the only concrete result was a promise: a large-scale exchange of prisoners of war, confirmed by both Moscow and Kyiv, that could happen soon. On the larger question, how to end a war that is nearly five years old, there was no breakthrough. American officials spoke of "openings", but offered little detail. The mood on each side differed sharply.

Davyd Arakhamia, a member of Ukraine's negotiating team, called it one of the hardest rounds so far, and the first since February. He believed the Russians had arrived with "very strict directives", which made any softening of positions extremely difficult. Even so, he sensed momentum and urged that a second round be organised quickly. Vladimir Medinsky, the Kremlin's negotiator, was less conciliatory.

In his telling, progress depends on Ukraine, on Washington, and on whether Europe "comes to its senses". Behind the diplomacy lies a contest over what European security should look like. Kyiv wants assurances that allies would help if it were attacked again, even without Nato membership. Moscow wants limits on the alliance's influence in eastern Europe, a grievance it has voiced since Nato's eastward expansion.