Can anyone explain why the mongols invaded russia?

It all started when Genghis Khan (1155-1227), the founder of the Mongol Empire, sent his son Jochi (1182-1227) to conquer the lands of what is now Siberia, Central Russia, and Eastern Europe. Giant armies of Mongol warriors (clearly over 100,000, an enormous number in the 13th century) easily defeated the weak and ill-numbered forces of the Russian princes, who were at war with each other before the invasion.

In 1237, the Mongols, led by Batu Khan, invaded Rus’. They took, ravaged and burned Ryazan’, Kolomna, Moscow, Vladimir, Tver – all the main Russian cities. The invasion continued until 1242 and was a terrible blow for the Russian lands – it took almost 100 years to fully recover from the damage the Mongol army did. Also, the lands and cities of the South – Kiev, Chernigov, Halych were burned to the ground. The North-Eastern lands, most notably Tver, Moscow, Vladimir, and Suzdal became the main cities after the invasion.

However, the Mongols didn’t want to conquer the land fully – they just wanted stable tributes. And they knew how to get what they wanted.

Explanation:

i'm assuming that the correct answer is indeed the first one/ "a"..