The Ottoman Empire was the sum of most of the nations in the Oriental civilization. As said in the post "Ethnic Cleansing in the Arab World" these nations lived in a patchwork of smaller and bigger areas between each other, the typical pattern in this civilization.
Since the dissolvement of this empire and its parallel Westernization began, more and more of these nations have become transformed into nations of the type normal in the Western civilization. And this implies the wish for a coherent territory for each nation.
This proces has happened through numerous etcnic cleansings. Beginning already in the 19th century in the Balkans, where the development restarted several times up to the 1990s. Continuing with the genocide of the Armenians and after the war with Greece the expelling of Turks and Greeks from Greece and the now reduced Turkey.
But Turkey continued to house miliions of Kurds. The policy towards these was one of forced assimilation in culture and language. This is another form of ethnic cleansing. It resulted in oppression and resistance, including the war with PKK, which used guerrilla-war and also terrorism though on a level infinitely smaller than that of the later IS.
The long running peace process with PKK gave hope that this conflict would be ended. Both kurds and Turks had become quite Westernized and therefore they were ready to live in a modern state where national difference did not matter as much as before. This would have been the last and third stage in the development from Oriental to modern Western nations after 1) patchwork nations and 2) ethnic cleansing. In this last stage like in modern Western countries there is room for more peoples.
But now after the last elections the AKP has ended the peace process and started extensive bombings. Of course provocations from PKK has also played a role. But from this to a full scale war there is a difference. Also worrying are the beginning measures against the legal party HDP, which has electoral support from Kurds, but also other people. The party could thus have pointed to a future modern Turkey, the mentioned third stage.
The changes in policy from Ankara looks like a return to the old policy against the Kurds seing them as an alien element. I do certainly not claim that Erdogan's purpose is renewed ethnic cleansing. Rather the purpose is to remove the Kurds as a political factor robbing AKP of their absolute majority. But ethnic tensions will inevitably rise as a result. PKK will answer with more violence. Mutual ethnic hatred between Turks and Kurds could rise once more.
The consequences for the war against IS is another chapter. But weakening PYD in Syria will definitely not help. A buffer-zone cannot be established without troops on the ground.