But halting progress, ever-more deadly drone attacks and unmoving negotiating positions seem to have taken their toll. On Thursday, Trump used a striking analogy to concede the warfare was nowhere near over, and that he did not, at that moment, feel it was best to intervene.

Russia’s Ministry of Internal Affairs said it had put Artyom Timofeyev, a Russian citizen who was born in Ukraine, on a national wanted list on suspicion of taking part in the attacks on Russian military airfields,