The Byzantine Empire originated and took its name after the city of Byzantium (later renamed Constantinople), which initially belonged to the Eastern Roman Empire. When the Western part of the Roman Empire fell in 476, the Eastern part became a self-sufficient domain. Constantinople became the capital, and the territory was titled Byzantine Empire. The Byzantine Empire lived on due to its distinct difference from its Western counterpart: a more significant focus on commercial trade and more urban structure allowed it to withstand and prosper. Its strengths were especially apparent during the emperorship of Justinian, who was able to seize some of the adjacent European territories. However, upon his passing, the Byzantine Empire began to decline. Its Church separated from the Catholic Roman Church; throughout that time, the influence of Turks and Arabs in the area was strengthened. Eventually, the catholic Crusades of the 1100s led to the change of power, which was subsequently taken back by Byzantian exiles. This turmoil weakened the nation, so the empire was overtaken when the Ottoman Turks rose to power in the 1400s.
By the 1100s, the population in the Middle East has been in the ongoing wars of expansion of Muslim states for centuries. As a reaction to the spread of Islam, the Roman Catholic Church organized the military operation – the so-called Crusades – to prevent the expansion and regain control over the formerly Christian territories. Particular importance was given to several cities considered holy by both Christians and Muslims. Despite the Crusades’ widely varying and increasingly diminishing success, they have had a notable impact. In the short term, the Christians established Crusader-governed states, including Jerusalem, Nicaea, and Antioch, signed a treaty that allowed access of Christians to Jerusalem, and took over Constantinople. In the long term, the Crusades managed to slow down the spread of Islam and, potentially, prevented the western European territories from being taken over by the Muslim power. Additionally, establishing a Christian presence in the Middle East facilitated trade with Europe, both in terms of knowledge and material goods.