Yaroslav, the fourth son of the long-reigning Grand Prince of Vladimir, Vsevolod the Big Nest, and Maria Shvarnovna, had been sent by his father in 1200 to rule the town of Pereyaslav near the Kopchak steppes.

Six years later, he had been summoned by Halychian boyars to rule their city but could not effectively claim the throne.

Thereupon he was sent to take Ryazan, but the stubborn opposition of the inhabitants led to the city being burnt.

Vsevolod had sent Yaroslav to oppose Mstislav the Bold in Novgorod in 1209.

After several battles, the two princes made peace, whereby Yaroslav had married Mstislav's daughter.

Vsevolod, upon his deathbed in 1212, had bequeathed to his son Pereslavl-Zalessky.

In the conflict between his elder brothers Konstantin and Yuri, Yaroslav had supported the latter.

He had accepted the offer of the Novgorodians in 1215 to become their prince but, desiring revenge for their former treachery, had instead captured Torzhok and blocked its supplies of grain to Novgorod.

Several months later, he was defeated by his father-in-law on the Lipitsa River and had to retreat to Pereslavl (a helmet that he lost during the battle will be retrieved by archaeologists in 1808).

Finally enthroned in Novgorod, Yaroslav had in 1222 overrun all of Estonia and besieged its capital, Kolyvan.

He had devastated Finland four years later and forcibly converted Karelia to Christianity.

Yaroslav’s next ambition had been to subjugate Pskov, but the Novgorodians had refused to make war against its neighbor.

Yaroslav had departed in anger and seized the Novgorodian enclave of Volokolamsk.

In 1234, he had returned to Novgorod.

He follows Danylo of Halych's advice and moves from Novgorod to Kiev in 1236, leaving his son Alexander as his representative in the north.

The defeat at the Kalka River had left the Kievan principality at the mercy of invaders, but the Mongol forces had retreated, not to reappear for thirteen years, during which time the princes of Rus' have gone on quarreling and fighting as before, until they are startled by a new and much more formidable invading force.

The main Mongol force, headed by Jochi's sons, and their cousins, Möngke Khan and Güyük Khan, arrive at Ryazan in December 1237.

Ryazan refuses to surrender, and the Mongols sack it.

The Principality is completely overrun with almost the whole princely family killed and the capital completely destroyed; it will later be moved to another location.

Batu moves into central Russia in 1238 to subdue the Western Russian principalities.

Besieging Vladimir, he finally overruns it on February 8, 1238.

A great fire destroys thirty-two limestone buildings on the first day alone, while the family of Grand Prince Yuri II perishes in a church where they had sought refuge from the flames.

The grand prince himself manages to escape.

Yuri’, after the Mongols sack his capital, flees across the Volga northward to Yaroslavl', where he hastily musters an army.

He and his brothers then turn back toward Vladimir in hopes of relieving the city before the Mongols take it, but they are too late.

Yuri sends out a force of three thousand men under Dorozh to scout out the Mongols’ position; whereupon Dorozh returns saying that Yuri and his force are already surrounded.

As he tries to muster his forces, he is attacked by the Mongol force under Burundai and flees, but is overtaken on the Sit River and dies there along with his nephew, Prince Vsevolod of Yaroslavl'.

The battle marks the end of unified resistance to the Mongols and inaugurates two centuries of the Mongol domination of modern day-Russia, Ukraine, and Belarus.

Major cities such as Torzhok and …

…Kozel'sk are captured and burned.

Kozel'sk becomes famous when its seven-year-old prince Vasily, son of Titus, has to defend the town against the army of Batu Khan.

The latter dubs it an "evil town" because its citizens had been fighting the attackers for seven weeks in a row, killing around four thousand enemy soldiers during the siege.

The citizens of Kozel'sk are greatly outnumbered and almost all of them die in battle.

Yaroslav, following the battle death of his older brother, leaves Kiev for Vladimir, where he is crowned grand prince.

Some of the armed forces of Ryazan withdraw to unite with the Vladimir-Suzdal army and meet the forces of Batu Khan near Kolomna.

Batu advances toward Novgorod in 1239 but is forced to turn back  after becoming bogged down in a muddy spring thaw.

He rests throughout the remainder of 1239 until fresh Mongol troops and horses replenish the heavy losses of the recent campaigns.

The Mongols and Turkic auxiliaries under Batu attack the Alans and the Cumans in the steppe to the north of the Black Sea in 1239, driving some two hundred thousand Cumans west of the Carpathian mountains.