The internal war in south Russian land in 30-s of XIII century was the longest and the most violent one - the largest internal feudal strife in the history of medieval Russia. It began from the fight for Galich throne, which was passed to the son of Hungarian king according to the will of the Prince Mstislav Udaloy (died in 1228).
In 1233-1234 Daniil Romanovich Volynsky in alliance with Kiev prince Vladimir Rurikovich waged war against Hungarians, who were in the alliance with Chernigov Prince Mikhail Vsevolodich. In 1234 Daniil conquered Galich.
Next year Mikhail Chernigovsky with Izyaslav Mstislavich (most probably the son of Mstislav Udaloy) began military operations against Vladimir and Daniil, who couldn't have captured Chernigov and returned to Kiev. At the same time Izyaslav brought Polovtsy forces to Russia. Near Kiev Daniil and Vladimir were defeated, Vladimir was captured by the Polovtsy, and Izyaslav became the Prince of Kiev. Mikhail went to Galich land and captured Galich.
Vladimir was freed soon and became the Prince of Kiev again. But it wasn't possible for him to remain on the throne, so Vladimir and Daniil invited Novgorod Prince Yaroslav Vsevolodich to Kiev. Mikhail Chernigovsky had been the enemy of Yaroslav since long time - in 1229-1232 they had fierce struggle for Novgorod throne. In 1236 Yaroslav settled in Kiev. At the same time in Galich there was continuous war between Mikhail and Izyaslav on one side and Daniil and his brother Vasilke on the other side.
In winter of 1237-1238, Northeastern part of Russia was invaded by Baty's armies. The great Prince of Vladimir Yury Vsevolodovich (the elder brother of Yaroslav) was killed in the battle. In spring of 1238 Yaroslav left Kiev, went to the ruined Vladimir-Suzdal land and occupied the Vladimir throne. Mikhail made use of his enemies having weakened and captured Kiev, leaving his son Rostislav to reign in Galich. But Daniil managed to reconquer Galich the next year.
In the autumn of 1239, Mongol-Tatars ruined the land of Mikhail - Chernigov principality, and began to threaten Kiev. In winter of 1239-1240 Yaroslav began campaign to the south of Russia. Mikhail left Kiev right away, ran to Hungary, thus loosing everything he had. Rostislav Mstislavich ascended the throne, but Daniil soon dethroned him and settled Dmitr, his boyar, in Kiev. It was the eve of Baty khan campaign to Kiev.
During the internal war Russian princes exhausted their force. This and their dissociation played negative role in the face of coming Mongol-Tatar invasion.