East, though some historians refer to it with the catchall term Nestorian Church despite the fact that many eastern Christians were not following the doctrine preached by Nestorius. Expansion to Sogdiana and eastern Central Asia Proselytism, combined with sporadic Sassanian persecutions and the exiling of Christian communities in their own area, caused the spread of Christianity to the east. The Edict of Milan in 313, granted Christianity toleration by the Roman Empire. After the Emperor Constantine's conversion to Christianity, the indigenous Christians of Persia were considered a political threat to the Sassanians. They exiled Christian communities to the east, such as a community of Orthodox Melkites who were installed in Romagyri near Tashkent, or a community of Jacobites, who were sent to Yarkand in the Xinjiang at the doorstep of China. The Hephthalites are known to have been open somewhat to Christianity since 498, and they requested the Nestorian Catholicos to establish a diocesan bishop in their lands in 549. By 650, there were 20 Nestorian dioceses east of the Oxus river. The development of Islam in the late 7th century further cut off Asian Christianity from the Western Christians, but eastern expansion of the faith continued nonetheless. Relations with Islam were good enough for the Catholicos to leave Seleucia-Ctesiphon to set up his seat in Baghdad upon the establishment of the Abbassids in 750. From the 7th century onward, the nomadic Turks of Central Asia started to convert to Nestorian Christianity. Mass conversions are recorded in 781−2 and later in 1007, when 200,000 Turks and Mongols reportedly became Christians. The Turkish Kipchaks are also known to have converted to Christianity at the suggestion of the Georgians as they allied in their conflicts against the Muslims. A great number were baptized at the request of the Georgian king David II. From 1120, there was a Kipchak national Christian church and an influential clergy. Early Christianity in China Christianity may have existed earlier in China, but the first documented introduction was during the Tang dynasty (618–907) A Christian mission under the leadership of the priest Alopen (described variously as Persian, Syriac, or Nestorian) was known to have arrived in 635, where he and his followers received an Imperial Edict allowing for the establishment of a church. In China, the religion was known as Dàqín Jǐngjiào (大秦景教), or the Luminous Religion of the Romans. 大秦 Dàqín designates Rome and the Near East,