Later on, the Russian presence strengthened and the highlanders of Western Caucasia were finally subjugated by Russia in 1864. The autonomy of Abkhazia, which had functioned as a pro-Russian "buffer zone" in this troublesome region, was no longer needed by the Tsarist government and the rule of the Shervashidze came to an end; in November 1864, Prince Michael was forced to renounce his rights and resettle in Voronezh. Later that same year, Abkhazia was incorporated into the Russian Empire as a special military province of Sukhum-Kale which was transformed, in 1883, into an ''okrug'' as part of the Kutais Governorate. Large numbers of Muslim Abkhazians, said to have constituted as much as 40% of the Abkhazian population, emigrated to the Ottoman Empire between 1864 and 1878 with other Muslim population of Caucasus, a process known as ''Muhajirism''.