Answer:
Russian & Mongol cooperation in the Middle Ages
Explanation:
Roughly from the 11th century on, orthodox Cristianity spread east & north wards in medieval Europe. By 1200 it had reached the Kievan Empire, that in its heydays spread from the Caspean to the Baltic Sea. If I´m not mistaken Novgorod is a place east from the Baltic States, close to St. Petersburg. Now, in the 1200s Mongol invaders (Tatars) swept out of Central Asia and conquered Kiev. But they allowed Russian princes to rule over local states. So they worked together and the orthodox christian people were the victims.