Medieval Russia
Church of Yuriev-Polsky (1200's)
But in the 1200's Russia was weak from civil wars, and the Mongols attacked Russia and forced the eastern part into the Mongol empire. Poland and Lithuania conquered the western part of Russia. In addition, knights from the Holy Roman Empire (modern Germany) kept invading too!
The Mongol empire made it even easier to trade across Asia, and the Russians continued to get rich from this trade. But in the early 1300's, the trade brought plague germs to Russia too, and the Black Death killed many people, and also spread to Europe. This weakened the Mongol Empire so that it collapsed, and the Russians gradually got free again.
By the time Constantinople fell to the Ottomans in 1453 AD, Russia was becoming an independent country again. Now that there was no Christian emperor in Constantinople anymore, the Russian kings thought they should take over, and so they began to call themselves Caesars, like the Roman Emperors. In Russian, Caesar came out as Czar or Tzar.
