In February, 2016, Pope Francis, en route to Mexico, made a diplomatic stop in Havana. The stop lasted just a few hours, and he never left the airport. In a gussied-up V.I.P. room in a cargo hangar, he met with Kirill, the Patriarch of Russian Orthodox Christianity. The long-sought encounter was the first between the leaders of the two Churches since the Great Schism of 1054. Kirill had refused to meet in Europe, citing "open wounds" in Orthodoxy’s dealings there; Francis had said, "I will go where you wish," so they wound up in Havana. They signed a joint declaration affirming common aims, such as the defense of traditional marriage, and deploring "hostility" and developments, such as the "confrontation" in Ukraine -- a reference to fighting in the Crimea and in the Donbas after the Russian military moved on those regions. And they held out the prospect of meeting again -- say, during a papal visit to Moscow.