How does the byzantine empire fit the theme of state building and expansion (227) ?

Note that the Byzantine Empire was the continuation of the Roman Empire, having been a part of the eastern section that have Constantinople as its capital. It survived as the western part deteriorated from attacks by Germanic tribes. The Byzantine part was more urbanized, was better in terms of financial capability, and had able rulers in its early years (notably Anastasius I and Justinian I). With money and established government, it became easy for Byzantine Empire to build a state and fend of enemies for a while using tributes and hiring mercenaries. It began to expanding again during the reign of Basil I in year 867, reconquering territories it lost during past years.