The Crusades differ from any other period in European history. The one main feature that distinguishes this mediaeval epoch from other periods is that The Crusades were religious warfare between Christianity and Islam. Since the Middle Ages, the word "crusade has been meant to include all wars undertaken in pursuance of a vow, and directed against infidels, or those under the ban of excommunication. The origin of the Crusades can be directly traced back to the moral and political condition of Western Christendom in the eleventh century. At that time, Europe was divided into numerous states whose sovereigns were absorbed in tedious and petty territorial disputes while the emperor, in theory the temporal head of Christendom, was wasting his strength in the quarrel over Investitures. It has been customary to describe the Crusades as eight in number with the eighth crusade being fought in 1270. However, this division is subjective and excludes many important expeditions including those in the fourteenth and fifteenth centuries. The Crusades actually continued until the end of the seventeenth century. Historical works summarize the history of the Crusades from the events leading up to the first Crusade in 1095 to the cultural influences the Crusades have had on modern times. A comparison of several research works by historians show that the Crusades of the Medieval times changed the way the world now looks at Christianity. A review of these works reveals the different approaches used to chronicle the key people and events that influenced the Crusades and gives the reader an insider's view on the events that caused these religious wars.
The Crusades by Richard A. Newhall provides a chronological evaluation of the development of the Crusades and discuses in depth each separate religion's part in one of the Crusades. Newhall relies primarily the religious and political causes of the Crusa