Developments in the legal and religious fields in the Empire led to adaptations that heavily influenced medieval Europe. In the legal field, Justinian's codification of Roman law produced the body of work called the ‘corpus iuris civilis' (Body of the Civil Law) which became the inspiration and foundation of civil law in most of western Europe. It was in the Empire that the intertwining of church and state took roots as Caesaropapism. It was the emperor Constantine which adopted Christianity and the following emperors who preserved it as a part of empire. This model was propagated by the Roman Church into Western Europe but for the most part of the Middle Ages, the Roman Catholic pope held sway over the religious and political life of Europe at the time.
In government, the Empire introduced the concept of military civil administration which proved effective in governing large territories that it was followed by future world powers like England and Spain. This was the concept of the theme (imperial province) which was ruled by a general who is responsible for military defense and local government. The concept of quick mobilization of citizens for combat duty found expression in the dual role of small land-holding peasants in being farmers in peacetime and soldiers when wars are at hand. It was also here that land ownership was used as a motivation for peasants to render military service. Future rulers of Western Europe would practice promising land and spoils to soldiers who conquer new territory.
The Empire made the most of its central location to demonstrate the economic advantages of controlling trade routes. It was able to impose customs duties and acquire goods from all trade destinations. The concept of banking and insurance was also implemented and became basic economic practices in the future world.