They wanted to expand their borders.
Immigrants can enrich a nation. But there is a difference between immigrants and colonists. The former are eager to learn<span> the ways of their adopted home, to integrate and perhaps assimilate — which does not require relinquishing their heritage or forgetting their roots. Colonists, by contrast, bring their culture with them and live under their own laws. Their loyalties lie elsewhere.</span>
Answer:
The Byzantines sent wave after wave of christian missionaries to the Slavic lands, which sorrounded the Byzantine Empire.
Two of the most important missionaries were Saint Cyril and Saint Methodious. They were brothers, and converted many slavs to Orthodox Christianity, specially those living in Moravia. They also invented the cyrilic alphabet to give a script to the Slavic languages, and help spread christianity faster. Hence the name of the alphabet.
