The correct answer is D) They managed to conquer Russia during the winter.
The impressive feat that the Mongols accomplished in Russia was that they managed to conquer Russia during the winter.
Yes, that was an amazing feat because although the Mongols were known to be fierce warriors and had an impressive army, the harsh cold winter of Russia can be extreme. No big deal for the Mongols and the great strategies to fight a war.
Historians considered that the army that invaded Russia consisted of approximately 150,000 soldiers
From Turkey to Hungary, the Mongols decided to attack and capture the region of Kiev after winning every battle.