The Mongol Invasion of Ancient Rus'

The heroic resistance of the Russian soldiers and local villagers against the Mongol invaders in the winter 1237-38 period showed that although they had superior forces and the Slavs were fragmented, the Mongols couldn't conquer the whole of north-east Ancient Rus'. They were forced to return to the steppe before they came within 100km of Novgorod and then spent more than two years rebuilding their forces for new conquests.