The fall of the Byzantine Empire began as early as 634 A.D. when Muslim armies attacked and entered Syria. At the end of the 11th century, during the Crusades, there was growing animosity between Byzantium and the West. The final fall came in 1453 when Constantinople was conquered by an attack by an Ottoman army.
The Roman emperor Constantine built a "new Rome" on the former Greek colony of Byzantium and made Constantinople his capital in 330 A.D. Although during his reign there was unity, in 364 A.D., Emperor Valentinian divided the kingdom into western and eastern regions. The western region fared poorly and was under constant attack. In 476 A.D., Odoacer defeated the Roman Emperor Romulus Augustus, and Roman control over the western region effectively ended.
The eastern half of Byzantium flourished for another 1,000 years and created a rich culture of art, learning and literature. The Emperor Justinian I, who ruled from 527 A.D. until his death in 565 A.D., was among the empire's greatest Roman rulers, and his territory included most of the land around the Mediterranean Sea. Great monuments, such as the Church of Holy Wisdom and the Hagia Sophia, were built during this period of time. After Justinian's death, the empire found itself with large war debts, and the citizens were forced to pay heavy taxes. The army also did not have the resources to protect the territories acquired during Justinian's rule. Byzantium also faced attacks by the Slavs and Persians, political instability and damaging attacks in 634 A.D. from Muslim armies who entered Syria. Byzantium lost North Africa, Syria, the Holy Land and Egypt to Islamic armies.
In 1204, Constantinople was conquered by the Fourth Crusade, and an unstable Latin regime was established. Many refugees escaped to Nicaea to join the exiled Byzantine government and successfully overthrew Latin rule in 1261. However, the economy and the empire were permanently crippled. In 1369, Emperor John V failed to get financial aid from the West in order to shake off numerous threats from the Turkish Empire. He was arrested and forced to make Byzantium a vassal of the Turkish Empire. On the May 29, 1453, an Ottoman army stormed Constantinople, and Emperor Mehmed II entered the Hagia Sophia. Emperor Constantine XI died in battle on that day, and the great Byzantine Empire was no more.