Why was western Europe more united in 400 then it the 800?

Western Europe was not more united in 400 than in 800. In fact, it was much more disunited in 400.

In 400, the Western Roman Empire had collapsed and Europe was divided into a number of small kingdoms and duchies. These kingdoms and duchies were often at war with each other, and there was no central authority to enforce peace or order. In contrast, in 800, the Carolingian Empire had been established and was able to provide a degree of unity and stability to Western Europe. The Carolingian Empire was ruled by a single emperor, who was recognized as the supreme authority by the other rulers of Europe. The empire was also able to defend itself against external threats, such as the Vikings and the Muslims.

There are a number of reasons why Western Europe was more disunited in 400 than in 800. First, the collapse of the Western Roman Empire created a power vacuum in Europe that was filled by a number of different groups, including the Germanic tribes, the Celts, and the Basques. These groups had different languages, cultures, and traditions, and they were often in conflict with each other. Second, the Christian Church was still in its early stages of development, and it had not yet become the unifying force that it would later become. Finally, the geography of Europe made it difficult for the different regions to communicate and cooperate with each other.

In contrast, by 800, a number of factors had contributed to the greater unity of Western Europe. The Carolingian Empire had been able to establish its authority over much of Europe, and the Christian Church had become a powerful force for unity. In addition, the geography of Europe had become more accessible, thanks to the development of new transportation technologies.

As a result of these factors, Western Europe was much more united in 800 than in 400. This unity would continue to grow in the centuries to come, and it would eventually lead to the emergence of the modern nation-state.