Final answer:
During the Viking era, the main Christian empires were the Byzantine Empire and the emerging Holy Roman Empire, while the main Islamic empires were the Abbasid Caliphate and the Umayyad Caliphate extending into Spain.
Step-by-step explanation:
The Viking era, which spanned from the late 8th century to the late 11th century, was a period of significant activity for both Christianity and Islam. Historically, the main empires associated with Christianity during this time were the Byzantine Empire and the nascent Holy Roman Empire, which arose in what is now considered central Europe.
As for Islam, the most prominent empires were the Abbasid Caliphate, which controlled a vast region from its center in Baghdad, and the Umayyad Caliphate, particularly its extension in Al-Andalus or Muslim Spain. These Islamic empires marked the Golden Age of Islam, renowned for their advancements in science, medicine, and philosophy.
The interactions between the Vikings and these empires were multifaceted, encompassing trade, warfare, and cultural exchanges. Vikings from Scandinavia established trade routes extending into territories of both empires and even served as the Varangian Guard in the Byzantine court. With time, the Vikings themselves began converting to Roman Christianity, integrating into the European Christian culture while retaining many of their own traditions.