The Eastern Roman Empire (later known as the Byzantine Empire, and also known at the time as Romania, Roman Empire and روم (Rûm "Rome")) is a continuation of the Roman Empire in the east. Centered on its capital of Constantinople, and ruled by Emperors in direct succession to the ancient Roman Emperors. The Empire preserved Romano-Hellenistic traditions, but due to the increasing predominance of the Greek language, it became known to most of its western and northern contemporaries usually as the Empire of the Greeks.
During most of its existence the Empire has remained one of the most powerful economic, cultural, and military forces in Europe, despite setbacks and territorial losses, especially during the Roman–Persian and Byzantine–Arab Wars. It would suffer again during the 960's losing its territory on the Italian mainland, and again in the Second Crusade where its border territory would be split up between the Abbasid Caliphate and Crusader States belonging to several European nations. It did however, successfully annex the Bulgarian Empire in 1018 bringing the Balkan Peninsula back under its banner. While the Remnant War would continue in favour of the Crusaders, the Byzantine Empire would see little of its land returned.
Below, a map of the Byzantine Empire in 1025 AD, prior to the Second Crusade.