After the destruction of the Mordvin Inäzor Obram administrative centre and fillfort named Obran Osh (Ashli) at the site of future stone Kremlin in 1220, a small Russian wooden hillfort was founded by Grand Duke Yuri II of Russia in 1221. Located at the confluence of two most important rivers of his principality, the Volga (Mordvin "Rav" or "Rava"), and the Oka, and Obran Osh was renamed Nizhny Novgorod. Its name literally means Lower Newtown, to distinguish it from the older Novgorod. Its independent existence was threatened by the continuous Mordvin attacks against it. The major attempt made by Inäzor Purgaz from Arzamas in January 1229 was repulsed, but after the death of Yuri II on March 4, 1238 at the Battle of Sit River the Mongols occupied the fortress and the remnants of small Nizhny Novgorod settlement which surrendered without any resistance in order to preserve what had been developed since Purgaz's attack eight years earlier. Later a major stronghold for border protection, Nizhny Novgorod fortress took advantage of a natural moat formed by the two rivers.
Along with Moscow and Tver, Nizhny Novgorod was among several newly-founded towns that escaped Mongol devastation on account of their insignificance, but grew into (great) centers in vassalic Russian political life during the period of the Tatar Yoke. With the agreement of the Mongol Khan, Nizhny Novgorod was incorporated into the Vladimir - Suzdal Principality in 1264. After 86 years its importance further increased when the seat of the powerful Suzdal Principality was moved here from Gorodets in 1350. Grand Duke Dmitry Konstantinovich (1323-1383) sought to make his capital a rival worthy of Moscow; he built a stone citadel and several churches and was a patron of historians. The earliest extant manuscript of the Russian Primary Chronicle, the Laurentian Codex, was written for him by the local monk Laurentius in 1377.