IN JULY, President Obama said he had been “encouraged” by a telephone call Russian President Vladimir Putin had initiated to discuss Syria. The Russians, Mr. Obama confidently declared, “get a sense that the Assad regime is losing a grip over greater and greater swaths of territory” and “that offers us an opportunity to have a serious conversation with them.” Not for the first time, Mr. Obama was supposing that Mr. Putin could be enlisted in a diplomatic settlement to the Syrian civil war along lines Washington and its Arab allies support. Not for the first time, the president appears to have badly misread the Russian ruler.