The vast Mongol(Tartar) army of around 40,000 mounted archers, commanded by Batu Khan and Subutai, crossed the Volga River and invaded Volga Bulgaria in late 1236.
It took them only a month to extinguish the resistance of the weak Volga Bulgars, the Cumans-Kipchaks and the Alans.

In November 1237, Batu Khan sent his envoys to the court of Yuri II of Vladimir and demanded his submission.
A month later, the Tartar hordes besieged Ryazan.
After six days of bloody battle, the city was totally annihilated and inhabitants slaughtered.
Alarmed by the news, Yuri II sent his sons to detain the invaders, but they were defeated and ran for their lives.
Having burnt down Kolomna and Moscow, the horde laid siege to Vladimir on February 4, 1238.
Three days later, the capital of Vladimir-Suzdal was taken and burnt to the ground.
The royal family perished in the fire, while the grand prince retreated northward.
Crossing the Volga, Vladimir mustered a new army, which was encircled and totally annihilated by the Mongols in the Battle of the Sit River on March 4.

Thereupon Batu Khan divided his army into smaller units, which ransacked fourteen cities of modern-day Russia: Rostov, Uglich, Yaroslavl, Kostroma, Kashin, Ksnyatin, Gorodets, Galich, Pereslavl-Zalessky, Yuriev-Polsky, Dmitrov, Volokolamsk, Tver and Torzhok.
Chinese siege engines were used by the Mongols under Tului to raze the walls of Rus' cities.
The most difficult to take was the small town of Kozelsk, whose boy-prince Vasily, son of Titus, and inhabitants resisted the Mongols for seven weeks, killing 4,000.
As the story goes, at the news of the Mongol approach, the whole town of Kitezh with all its inhabitants was submerged into a lake, where, as legend has it, it may be seen to this day.
The only major cities to escape destruction were Novgorod and Pskov.
The Mongols planned to advance on Novgorod, but the principality was spared the fate of its brethren by the wise decision to preemptively surrender.

In mid-1238, Batu Khan devastated the Crimea and pacified Mordovia.
In the winter of 1239, he sacked Chernihiv and Pereiaslav.
After many days of siege, the horde stormed Kiev in December 1240.
Despite the resistance of Danylo of Halych, Batu Khan managed to take two of his principal cities, Halych and Volodymyr-Volynskyi.
The Mongol Tartars then resolved to "reach the ultimate sea", where they could proceed no further, and invaded Hungary (under Batu Khan) and Poland (under Baidar and Kaidu).
Batu Khan captured Pest, and then on Christmas Day 1241, Esztergom.
The vast Mongol(Tartar) army of around 40,000 mounted archers, commanded by Batu Khan and Subutai, crossed the Volga River and invaded Volga Bulgaria in late 1236. It took them only a month to extinguish the resistance of the weak Volga Bulgars, the Cumans-Kipchaks and the Alans.
In November 1237, Batu Khan sent his envoys to the court of Yuri II of Vladimir and demanded his submission. A month later, the Tartar hordes besieged Ryazan. After six days of bloody battle, the city was totally annihilated and inhabitants slaughtered. Alarmed by the news, Yuri II sent his sons to detain the invaders, but they were defeated and ran for their lives. Having burnt down Kolomna and Moscow, the horde laid siege to Vladimir on February 4, 1238. Three days later, the capital of Vladimir-Suzdal was taken and burnt to the ground. The royal family perished in the fire, while the grand prince retreated northward. Crossing the Volga, Vladimir mustered a new army, which was encircled and totally annihilated by the Mongols in the Battle of the Sit River on March 4.
Thereupon Batu Khan divided his army into smaller units, which ransacked fourteen cities of modern-day Russia: Rostov, Uglich, Yaroslavl, Kostroma, Kashin, Ksnyatin, Gorodets, Galich, Pereslavl-Zalessky, Yuriev-Polsky, Dmitrov, Volokolamsk, Tver and Torzhok. Chinese siege engines were used by the Mongols under Tului to raze the walls of Rus' cities. The most difficult to take was the small town of Kozelsk, whose boy-prince Vasily, son of Titus, and inhabitants resisted the Mongols for seven weeks, killing 4,000. As the story goes, at the news of the Mongol approach, the whole town of Kitezh with all its inhabitants was submerged into a lake, where, as legend has it, it may be seen to this day. The only major cities to escape destruction were Novgorod and Pskov. The Mongols planned to advance on Novgorod, but the principality was spared the fate of its brethren by the wise decision to preemptively surrender.
In mid-1238, Batu Khan devastated the Crimea and pacified Mordovia. In the winter of 1239, he sacked Chernihiv and Pereiaslav. After many days of siege, the horde stormed Kiev in December 1240. Despite the resistance of Danylo of Halych, Batu Khan managed to take two of his principal cities, Halych and Volodymyr-Volynskyi. The Mongol Tartars then resolved to "reach the ultimate sea", where they could proceed no further, and invaded Hungary (under Batu Khan) and Poland (under Baidar and Kaidu). Batu Khan captured Pest, and then on Christmas Day 1241, Esztergom.
Mongol invasion of Kievan Rus'