Kurdification is a cultural change in which non-ethnic Kurds or/and non-ethnic Kurdish area becomes Kurdish. This can happen both naturally (as seen in Turkish Kurdistan) and deliberately (as seen in Iraq after the invasion of Iraq).
The notion of kurdification is different from country to country. In Turkish Kurdistan, many ethnic Armenians, Bulgarians, Circassians, Chechens, Georgians, Ingushs, and Ossetians have become kurdified, as a result of fleeing to the region and having subsequently interacted with ethnic Kurds.
Caucasian refugees (1860s-1910s)
When refugees from Caucasus reached the Ottoman Empire, Constantinople decided not to settle these in Kurdistan due to the extreme poverty and lack of material resources for the refugees. Yet after some time, the Ottomans started seeing the refugees as a chance to diminish the Kurdish claim to the region and allowed the refugees to settle in the region. In 1862, Circassian refugees from the Shapsug tribe arrived in the Kurdish areas of Ahlat and Adilcevaz and settled in the three Kurdish villages of Yoğurtyemez, Xanik (Çukurtarla), Develik and founded the village of Koxiş (Yolçatı).
The first big wave of Caucasian refugees to Kurdistan was in 1864 when 15,000 to 20,000 refugees settled in Sarıkamış, founding new villages and settling in abandoned Greek and Armenian villages. These refugees included Circassians, Chechens, Laks and Avars. The largest group of refugees were Circassias who fled the Circassia region (part of the Russian Empire) during the ethnic cleansing of Circassians. Two years later, Shapsug tribe with members of the Abzakh tribe founded the villages of Bolethan (Karapolat), Arnis (Güzgülü) and Ximsor (Eskibalta) near Bingöl. Concurrently with the Circassian migration, Ossetians settled in the villages of Xulik (Otluyazı) and Ağcaviran (Akçaören) in Ahlat, Yaramış, Karaağıl, Hamzaşeyx (Sarıpınar), Simo (Kurganlı) in the eastern Muş region, and Lekbudak (Budaklı) near Karaçoban. According to the Russian intelligence officer Aleksandr Kolyubakin, no less than 1,500 Ossetians lived in the Sanjak of Muş in the late 1880s.
Chechens and Ingushs mostly settled in Varto area, in the villages of Arincik (Kıyıbaşı), Çarbuhur (Bağiçi), Tepeköy, Artet (Serinova), Ulusırt and Arinç (Çöğürlü), Avars who settled in Kayalık village, and Circassians of the Kabardian tribe founded the village of Narlı Çerkezleri (Eskinarlı) in Pazarcık area. There is also a Georgian village in Diyarbakir Province.
20th-21st century and PKK
When the Kurdish question rose in Turkey, it also had an effect on their Caucasian neighbours. Even today, there is an aversion from joining the Kurds in their conflict against the Turkish state, but many individuals of Caucasian origin joined the Kurdistan Workers' Party. As part of their campaign, the Kurdish party Peoples' Democratic Party won most Caucasian villages in Turkish Kurdistan.
Through the 20th century, an unknown number of Armenians living in the mountainous region of Tunceli (Dersim) had converted to Alevism. During the Armenian Genocide, many of the Armenians in the region were saved by their Kurdish neighbors. According to Mihran Prgiç Gültekin, the head of the Union of Dersim Armenians, around 75% of the population of Dersim are "converted Armenians." He reported in 2012 that over 200 families in Tunceli have declared their Armenian descent, but others are afraid to do so. In April 2013, Aram Ateşyan, the acting Armenian Patriarch of Constantinople, stated that 90% of Tunceli's population is of Armenian origin.
Until 2011 (end of main U.S. military presence)
The Kurdish government defended the Kurdification with the implementation of article 140 of the Iraqi constitution which ensured the restoration of the situation as it was before Saddam Hussein's genocide and Arabization policies against the Kurdish population during the Al-Anfal Campaign and the Kurdish Feyli genocide.
Intensified tensions between Kurds and Sunni Arabs led to violent clashes between both of them since Saddam's Arabization and genocide campaigns against the Kurdish population in Iraqi Kurdistan. On 21 August 2006, Shabak Democratic Party leader Hunain Qaddo proposed the creation of a separate province within the borders of the Nineveh Plains, in order to combat the "Arabization" and "Kurdification" of Iraqi minorities. The Iraqi government voted against the proposition.
Some Assyrians in the Iraqi Kurdistan region complained that construction plans were "aimed at affecting a demographic change that divides Assyrian blocs". In addition, some Yazidis, Shabaks and Turkmen have reported that a policy of cultural and security control was being implemented against them, especially in areas which belonged to the Kurds before Saddam's Al-Anfal Campaign.
In 2016, David Romano, Professor of Middle East Politics, said that without the YPG and Peshmerga, the Assyrians of northern Syria and Iraq would likely all be dead, lying in some jihadist-dug mass grave.
The United States Holocaust Memorial Museum published news which argued that the Yazidis have frequently been pressured to assimilate to both Arab and Kurdish ethnicities. Other sources have stated that Yazidis already speak Northern Kurdish which is one of the two major dialects of Kurdish language. 
Gareth Stansfield claimed Kurdification or re-Kurdification (post-Saddam) has been an open policy of the Kurdistan Regional Government (KRG) in Iraq since 2003.
During the Iraqi civil war, Iraqi army troops fled their posts around the Nineveh Plains while ISIL attacked. Later, KRG forces, with the support of coalition airstrikes, captured these areas from ISIL. Since then, there have been disputes between pro-government Assyrians and Kurds, as the former have either asked the Kurds to leave or promised them autonomy.
In 2011, some Yazidi activists voiced their "concern over forced assimilation into Kurdish identity". Some have accused the Kurdish and Iraqi parties of diverting US $12 million of reconstruction funds allocated for Yazidi areas in Jebel Sinjar to a Kurdish village and marginalizing them politically. According to Sweden-based economist David Ghanim, the goal of some tactics of the KRG had been to push Shabak and Yazidi communities to identify as Kurds, which has been strongly denied by KRG authorities. He also claimed that the Kurdish authorities are working to impose Kurdish identity on the Yazidis and the Shabaks.
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