Complex sentence: During the reign of the 18th Abbassid Caliph Al-Muqtadir, many Manichaeans fled from Mesopotamia to Khorasan from fear of persecution by him and about 500 of them assembled in Samarkand and the base of the religion was later shifted to this city.
Split into simpler sentences: During the reign of the 18th Abbassid Caliph Al-Muqtadir, many Manichaeans fled from Mesopotamia to Khorasan from fear of persecution by him and about 500 of them assembled in Samarkand. The base of the religion was later shifted to this city.