Soldiers who took part in this war wore crosses, so they were called crusaders. Crusaders mainly occupied Muslim-ruled West Asia through Roman Catholic forces and established some Christian countries, so they were also figuratively compared to "the cross against submission"; But it also involves the conquest of "Christian heresy", other heretics and "hostile forces" against other Catholic churches and feudal lords. For example, the goal of the Fourth Crusade was the orthodox Byzantine Empire.
Catholics believe that the original purpose of the Crusade was to recover Jerusalem, the holy land ruled by Muslims. When the Turkish Muslims in Denzel won the military victory over the Christian Byzantine Empire in Anatolia, the Crusades were ignited in response to Byzantium's request for help.
Long-term battles have been fought intermittently in the Levant, and the boundaries between enemies and friends in the war are not completely defined by religion. For example, Christians allied themselves with the Sultanate of Rome during the Fifth Crusade. Although the crusaders took defending religion and liberating the holy land as their slogan, they actually took political, social and economic purposes as their main purpose, accompanied by a certain degree of plunder.
Every group participating in the Crusade has its own purpose. Even in the fourth Crusade in 1204, Constantinople, the capital of Byzantine Catholic brothers and Orthodox Church, was looted. Therefore, Judith M. bennett, an American scholar, wrote in his book "History of Middle Ages in Europe" that "the Crusaders brought together three major upsurge at that time: religion, war and greed". By 129 1, Akka, the last bridgehead of the Christian world on the Syrian coast, was captured, and the fate of the Crusader countries ended.