Sergius of Radonezh blessing Dmitry Donskoy in Trinity Sergius Lavra, before the Battle of Kulikovo. The most powerful successor state to Kievan Rus' was the Grand Duchy of Moscow ("Moscovy" in the Western chronicles), initially a part of Vladimir-Suzdal. While still under the domain of the Mongol-Tatars and with their connivance, Moscow began to assert its influence in Western Russia in the early 14th century.