while the Novgorod Republic continued to prosper in the north. In the northeast, the Byzantine-Slavic traditions of Kievan Rus' were adapted to form the Russian autocratic state. Grand Duchy of Moscow The destruction of Kievan Rus' saw the eventual rise of the Grand Duchy of Moscow, 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 the region in the early 14th century, gradually becoming the leading force in the "gathering of the Russian lands". When the seat of the Metropolitan of the Russian Orthodox Church moved to Moscow in 1325, its influence increased. Moscow's last rival, the Novgorod Republic, prospered as the chief fur trade centre and the easternmost port of the Hanseatic League. Led by Prince Dmitry Donskoy of Moscow, the united army of Russian principalities inflicted a milestone defeat on the Mongol-Tatars in the Battle of Kulikovo in 1380. Moscow gradually absorbed its parent duchy and surrounding principalities, including formerly strong rivals such as Tver and Novgorod. Ivan III ("the Great") finally threw off the control of the Golden Horde and consolidated the whole of northern Rus' under Moscow's dominion, and was the first Russian ruler to take the title "Grand Duke of all Rus'". After the fall of Constantinople in 1453, Moscow claimed succession to the legacy of the Eastern Roman Empire. Ivan III married Sophia Palaiologina, the niece of the last Byzantine emperor Constantine XI, and made the Byzantine double-headed eagle his own, and eventually Russia's, coat-of-arms. Vasili III completed the task of uniting all of Russia by annexing the last few independent Russian states in the early 16th century. Tsardom of Russia In development of the Third Rome ideas, the grand duke Ivan IV ("the Terrible") was officially crowned the first tsar of Russia in 1547. The tsar promulgated a new code of laws (Sudebnik of 1550), established the first Russian feudal representative body (the Zemsky Sobor), revamped the military, curbed the influence of the clergy, and reorganised local government. During his long reign, Ivan nearly doubled the already large Russian territory by annexing the three Tatar khanates: Kazan and Astrakhan along the Volga, and the Khanate of Sibir in southwestern Siberia. Ultimately, by the end of the 16th century, Russia expanded east of the Ural Mountains. However, the Tsardom was weakened by the long and unsuccessful Livonian War against