What other world powers did Charlemagne have political relationships with?

Charlemagne, the King of the Franks and later Emperor of the Romans, maintained political relationships with several world powers during his reign. He forged alliances with the Byzantine Empire, strengthening ties through diplomacy and marriage, especially with Empress Irene. His interactions with the Abbasid Caliphate also involved diplomatic exchanges and trade, reflecting a complex relationship marked by both rivalry and mutual respect. Additionally, he engaged with various Slavic tribes and other neighboring states to expand and consolidate his empire.