The Byzantine Empire, also known as the Eastern Roman Empire, was important to Western Europe for a number of reasons:
Cultural transmission: The Byzantine Empire acted as a bridge between the classical world of Greece and Rome and the medieval world of Europe. It preserved the literature, art, and philosophy of ancient Greece and Rome and transmitted it to Western Europe, where it had a profound impact on the Renaissance.
Trade: The Byzantine Empire was a major center of trade between Europe and Asia. It controlled the trade routes that connected Europe with the Silk Road, and its capital, Constantinople, was one of the most important trading cities in the world. Its wealth and commercial influence helped to shape the economies of Western Europe.
Military power: The Byzantine Empire was a powerful military force that protected Western Europe from the east. It served as a bulwark against the Muslim invasions of Europe and helped to prevent the spread of Islam into Western Europe. Its armies also fought alongside the armies of Western Europe in the Crusades. Overall, the Byzantine Empire's influence on Western Europe was multifaceted and far-reaching, shaping the cultural, economic, military, religious, and political landscape of Western Europe for centuries to come.