As the years went by, the Black Sea Cossacks continued its systematic penetrations into the mountainous regions of the Northern Caucasus. Taking an active part in the finale of the Russian conquest of the Northern Caucasus, they settled the regions each time these were conquered. To aid them, a total of 70 thousand additional ex-Zaporozhians from the Bug, Yekaterinoslav, and finally the Azov Cossack Host migrated there in the mid 19th century. All three of the former were necessary to be removed to vacate space for the colonisation of New Russia, and with the increasing weakness of the Ottoman Empire as well as the formation of independent buffer states in the Balkans, the need for further Cossack presence had ended. They made the migration to the Kuban in 1860. Separating the ethnic Ukrainian Black Sea Cossacks from the Caucasian mountain tribes were the Caucasus Line Cossack Host, ethnic Russian Cossacks from the Don region. Although both groups lived in the general Kuban region, they did not integrate with each other.