Ok, here's my area. I'm currently finishing my thesis on the economics of the slave trade between the Ottoman Empire and the North Black Sea system, more specifically the Crimean Khanate. As the Wikipedia article will tell you, the region has changed hands many times, most often between Slavic or Turkic peoples. The Genoese trade post of Caffa (Ottoman Kefe, later Feodosiya) existed as early as 1299 and ran a slave trade from Trebizond to Lithuania. Trade cities like these were key points of interaction between the Golden Horde and the Ottoman Empire. The trade of Turkic people's to the Ottomans and the larger Arab slave trade by the Italians was not always looked upon kindly by the Mongols and caused the city to be sacked several times. One incident in 1348 became famous for being a possible vector of infection for the Black Plague to Europe as the Mongols launched infected corpses over the wall. The Horde however began to decentralize and in the early 15th century the leader of the Giray clan was invited out of exile in Ruthenia to become Khan. Alan Fisher, a great historian of the Crimean Khanate, states that places like the Crimea had become great stages for Ghengisid successors to pull away from the Horde and establish their own sovereignty. This is precisely what the Giray clan did in the 1440s after a long war with the Horde. Within only a few decades the Khan Mengli Giray invited Mehmed II to provide Ottoman assistance in driving out the remaining Italian trade colonies in 1475. While the Ottomans were there (Key commander was Gedik Ahmet Pasa), Mengli Giray was captured and taken to Istanbul to pledge loyalty to the Sultan. This began an odd relationship very different from other states the Ottomans dealt with. According to Halil Inalcik, the Khan viewed himself as an Ottoman official (tikme) rather than a vassal lord. The Porte often slowly replaced local officials with Muslim Ottoman appointed officials in conquered territories. They obviously didn't do this in the Crimea as the Khanate was already an Islamic body. The Khan was allowed to maintain much of his autonomy, although much later we find the Sultan exercising veto power over Khanate succession. This was done for several reasons, my thesis argues is that the infamous slave raiding of the Khanate provided an increasingly large amount of the Porte's budget, creating a sort of dependency loop in which the Porte needed to ensure Crimean stability and the flow of slaves. Slave raiding by the Khans was so widespread that the Russian Empire established a separate Ulozheniye to collect slave ransom taxes for subjects of the Czar. This raiding is consistent and damaging to southern Russia until Peter the Great basically puts a stop to it. After the late 18th century the Crimean Tatars become less and less important to the region's economic system. Throughout the long 19th century and into the mid 20th century, the Tatars faced increasing amounts of conquest, cleansing, and deportation, at the hands of the Russian Empire, then the USSR. I am less versed in these events than I am early modern history, but I will say a quick look into the treatment of the Tatars post-Peter the Great by the Russian Empire and the USSR will quickly yield the back ground as to why the Tatars are not interested in rejoining Russia. Sources; Fisher, Alan. A Precarious Balance, Ibid. The Crimean Tatars, Inalcik, Halil, An Economic and Social History of the Ottoman Empire.