The knyazes' wars were only one of the troubles of Rus. The other was the tribes of the nomads in the steppes. We have said before that pechenegs were defeated by Yaroslav the Wise in 1034. Soon after that they left Rus completely to the Balkans. Another, stronger tribe took their place, the Polovtsians (Kipchak). Since 1061, their raids were incessant. They robbed the cities, killed or enslaved people. The slaves were sent to Crimea and then to other countries of Europe and Asia. Only in 150 years from 1061 to 1210 there were 50 especially large raids. Naturally, the southern parts of the country suffered most: Kiev, Pereyaslavl, Chernigov, etc. Sometimes even knyazes asked the nomads to assist them in the wars with other knyazes.
More often, though, the knyazes worked together to stop the nomads. So, during the Dolobsky congress of the knyazes, Monomakh managed to talk Svyatoslav Izyaslavich into a joint campaign and in 1103 they defeated the Polovtsians. With time, the attacks of the nomads grew stronger and in 1185 the Igor Svyatoslavich and Vsevolod Svyatoslavich, grandsons of Oleg Svyatoslavich, knyaz of Chernigov, were defeated and captured. This campaign, the battle, the defeat and Igor's escape from the captivity were described in chronicles and in the poetic legend called "The Tale of Igor's Campaign". Knyazhestvo of Pereyaslavl was almost lost in the second half of the XII century and the Polovtsians were not only invading it, but settled there. Russian city on the Azov sea, Tmutarakan, was lost and the southern roads were in the hands of the nomads. So, the trade with Greece declined and finally stopped completely. The importance of Kiev, based on its position as a "middleman" was also lost. By this time, after the crusades, European countries found other trade routes to the East and Kiev was depopulating and growing poor. The population of the southern parts of Rus fled from dangers and poverty to the north or to the west.