Unprecedented Situation
As a holy land of faith, Jerusalem had been destroyed by foreign peoples many times throughout history and rebuilt many times as well. It was a city watched by the entire world, yet plagued by misfortune and scarred by numerous wars.
Among them, the Crusades could be called a series of truly historic campaigns.
They were a series of famous religious military expeditions carried out with the permission of the Roman Catholic pope. Under the pretext of reclaiming the lands invaded and occupied by Arab Muslims, feudal lords and knights from Western Europe launched wars against the countries along the eastern Mediterranean coast. There were nine in total, lasting nearly two hundred years—hardly less enduring than the Hundred Years' War, known as the longest war in history.
Because the cross was the symbol of Christianity, every person who joined an expedition wore a cross-shaped mark on their chest and arm. Thus, they were called crusaders, and these religious military expeditions became known as the Crusades.
At that time, Jerusalem, originally a holy land of Roman Catholicism, had fallen into the hands of Islam. In order to reclaim the lost territory, Roman Catholicism launched multiple eastern expeditions.
However, in reality, the eastern expeditions were not limited to fighting Islam.
For example, during the Fourth Crusade, the target was the Byzantine Empire, which followed Eastern Orthodoxy. In the regions they occupied, the crusaders established dozens of crusader states, the largest of which was the Kingdom of Jerusalem. There were also the Principality of Antioch and the County of Tripoli, among others. As a result, the Crusades were passed down in praise throughout the Catholic world for generations. Numerous military chaplains and later church chroniclers did their utmost to record the campaign, praising Christ and spreading its story like a miracle.