In the 16th century, the Buryat Mongols migrated from northern Mongolia to the Lake Baikal region, which was conquered and made part of the Russian empire in the 17th century. One group of the Oirat western Mongols in northern present-day Xinjiang migrated to the Volga region of Russia in the early 17th century and became known as the Kalmyks. Those who stayed behind were decimated by the Manchus in the mid-17th century, but one group of Volga Kalmyks migrated back to Xinjiang toward the end of the 18th century. The people of Tuva are Turkic speakers but have traditionally studied in Mongolia and Tibet. They were conquered and ruled as part of the Manchu Qing empire, then after the fall of the Qing in the early 20th century, were an independent country, called Tannu Tuva, but then incorporated into the USSR after World War II. All these regions have traditionally followed the Gelugpa tradition of Tibetan Buddhism, as has been the case in Mongolia, but in 1990, there were only two monasteries with a handful of married “monks” in Buryatia and Chita, and none in Kalmykia or Tuva.