The Crusades were expeditions undertaken, in fulfilment of a solemn vow, to deliver the Holy Places from Mohammedan tyranny.
The origin of the word may be traced to the cross made of cloth and worn as a badge on the outer garment of those who took part in these enterprises. Medieval writers use the terms crux (pro cruce transmarina, Charter of 1284, cited by Du Cange s.v. crux), croisement (Joinville), croiserie (Monstrelet), etc. Since the Middle Ages the meaning of the word crusade has been extended to include all wars undertaken in pursuance of a vow, and directed against infidels, i.e. against Mohammedans, pagans, heretics, or those under the ban of excommunication. The wars waged by the Spaniards against the Moors constituted a continual crusade from the eleventh to the sixteenth century; in the north of Europe crusades were organized against the Prussians and Lithuanians; the extermination of the Albigensian heresy was due to a crusade, and, in the thirteenth century the popes preached crusades against John Lackland and Frederick II. But modern literature has abused the word by applying it to all wars of a religious character, as, for instance, the expedition of Heraclius against the Persians in the seventh century and the conquest of Saxony by Charlemagne.
The idea of the crusade corresponds to a political conception which was realized in Christendom only from the eleventh to the fifteenth century; this supposes a union of all peoples and sovereigns under the direction of the popes. All crusades were announced by preaching. After pronouncing a solemn vow, each warrior received a cross from the hands of the pope or his legates, and was thenceforth considered a soldier of the Church. Crusaders were also granted indulgences and temporal privileges, such as exemption from civil jurisdiction, inviolability of persons or lands, etc. Of all these wars undertaken in the name of Christendom, the most important were the Eastern Crusades, which are the only ones treated in this article.
If this is a plausible theory, then the terrorists are applying, in reverse, the Crusades against them towards us. What do you think about this idea?