The deepening ties were reflected when Putin flew to Tehran, in November, for talks with Supreme Leader Ali Khamenei and President Hassan Rouhani. “Our coöperation can isolate America,” Khamenei told Putin, according to Iran’s media. Putin called the growing Russian-Iran coöperation “very productive.”

Putin and Khamenei spent a highly unusual hour together, one on one, accompanied only by interpreters. “The most important thing that Putin said was, ‘I will not betray you,’ ” Ali Vaez, an Iranian-American who heads the Iran portfolio of the Brussels-based International Crisis Group, told me.