It is customary for Central Asian leaders to exchange pleasantries among themselves whenever one of their countries is marking a day of independence or some other major holiday. But the warmth that Turkmen President Serdar Berdymukhamedov conveyed in his message to his Uzbek counterpart, Shavkat Mirziyoyev, for September 1 was more than mere formality. It is hard to think which two nations in the region are at present enjoying as rosy a relationship as these two. As the data suggests, this cordial state of affairs is very much a legacy of…