When Sergius of Radonezh founded a monastery near Moscow, his example spawned a movement of monastic foundations throughout Russia. Within three decades of his death in 1392, Sergius was recognized as a saint, and by 1450 many considered him the intercessor for the Russian land who freed its people from Mongol rule. Over the next century and a half, thousands sought St. Sergius' intercession with gifts to the monastery. Moscow's rulers made...