The Bulgarian state existed before the formation of the Bulgarian people. Prior to the establishment of the Bulgarian state the Slavs had mingled with the native Thracian population. The population and the density of the settlements increased after 681 and the differences among the individual Slavic tribes gradually disappeared as communications became regular among the regions of the country. By the second half of the 9th century, Bulgars and Slavs, and romanized or hellenized Thracians had lived together for almost two centuries and the numerous Slavs were well on the way to assimilating the Thracians and the Bulgars. Many Bulgars had already started to use the Slavic Old Bulgarian language while the Bulgar language of the ruling caste gradually died out leaving only certain words and phrases.The Christianization of Bulgaria, the establishment of Old Bulgarian as a language of the state and the church under Boris I, and the creation of the Cyrillic script in the country, were the main means to the final formation of the Bulgarian nation in the 9th century; this included Macedonia, where the Bulgarian khan, Kuber, established a state existing in parallel with Khan Asparuh's Bulgarian Empire. The new religion dealt a crushing blow to the privileges of the old Bulgar aristocracy; also, by that time, many Bulgars were presumably speaking Slavic. Boris I made it a national policy to use the doctrine of Christianity, that had neither Slavic nor Bulgar origin, to bind them together in a single culture. As a result, by the end of the 9th century the Bulgarians had become a single Slavic nationality with ethnic awareness that was to survive in triumph and tragedy to present.