Byzantium was one of the greatest empires that ever existed. It reigned over extensive regions around the Mediterranean and in Eastern Europe from its founding by Constantine in 324 to the fall of Constantinople in 1453. During this period, its emperors had not only secular powers but also religious, dominating the Orthodox church that spread into Slavic lands. However, internal divisions, rivalry with the West, and the relentless battle against invaders, including the Ottomans, would eventually weaken the Byzantine Empire, and although it disappeared half a millennia ago, its influences can...