In the 13th century, the Mongols conquered Russia.
They occupied Russian lands and required Russian princes to pay tribute to them.
One prince emerged as more powerful than the others.
Alexander Nevsky, prince of Novgorod, defeated a German invading army in northwestern Russia in 1242.
The khan, leader of the western Mongol Empire, rewarded Nevsky with the title of grand prince and his descendents became princes of Moscow and eventually leaders of all Russia.