Rastislav the Great was a significant ruler of the Great Moravian Empire during the 9th century. He is best known for his efforts to strengthen the political and cultural unity of the Slavic people. Under his leadership, the empire expanded and became a center for trade and culture in Central Europe. Rastislav is also recognized for inviting the Byzantine brothers Cyril and Methodius to spread Christianity and develop a written Slavic language. Their work laid the foundation for the Cyrillic alphabet, which is still used in many Slavic countries today. Rastislav's reign marked a crucial period in the history of Slavic nations.