<P> Several attempts to negotiate the conflict went in vain and, in the meantime, George received reinforcements from the Kakhetians, and allied himself with the Byzantine commanders Nicephorus Phocas and Nicephorus Xiphias in their abortive insurrection in the emperor's rear . In December, George's ally, the Armenian king Senekerim of Vaspurakan, being harassed by the Seljuk Turks, surrendered his kingdom to the emperor . During the spring of 1022, Basil launched a final offensive winning a crushing victory over the Georgians at Svindax . Menaced both by land and sea, King George handed over Tao, Phasiane, Kola, Artaan and Javakheti, and left his infant son Bagrat a hostage in Basil's hands . </P> <P> Basil II is considered among the most capable Byzantine emperors and his reign as the apex of the empire in the Middle Ages . By 1025, the date of Basil II's death, the Byzantine Empire stretched from Armenia in the east to Calabria in Southern Italy in the west . Many successes had been achieved, ranging from the conquest of Bulgaria to the annexation of parts of Georgia and Armenia, and the reconquest of Crete, Cyprus, and the important city of Antioch . These were not temporary tactical gains but long - term reconquests . </P> <P> Leo VI achieved the complete codification of Byzantine law in Greek . This monumental work of 60 volumes became the foundation of all subsequent Byzantine law and is still studied today . Leo also reformed the administration of the Empire, redrawing the borders of the administrative subdivisions (the Themata, or "Themes") and tidying up the system of ranks and privileges, as well as regulating the behaviour of the various trade guilds in Constantinople . Leo's reform did much to reduce the previous fragmentation of the Empire, which henceforth had one center of power, Constantinople . However, the increasing military success of the Empire greatly enriched and empowered the provincial nobility with respect to the peasantry, who were essentially reduced to a state of serfdom . </P> <P> Under the Macedonian emperors, the city of Constantinople flourished, becoming the largest and wealthiest city in Europe, with a population of approximately 400,000 in the 9th and 10th centuries . During this period, the Byzantine Empire employed a strong civil service staffed by competent aristocrats that oversaw the collection of taxes, domestic administration, and foreign policy . The Macedonian emperors also increased the Empire's wealth by fostering trade with Western Europe, particularly through the sale of silk and metalwork . </P>

What was the center of the byzantine empire