Slovak history is marked by its early settlement by Celtic tribes and later by the arrival of the Slavs in the 6th century. The region became part of the Great Moravian Empire in the 9th century, which is significant for the introduction of Christianity and the Cyrillic alphabet. In the 20th century, Slovakia was part of Czechoslovakia, formed after World War I. Following World War II, it became a communist state within the Eastern Bloc. In 1993, Slovakia peacefully separated from the Czech Republic, becoming an independent nation, and has since developed its own identity and governance.