There were other considerations which made occasion for the crusades. Gregory VII preached a crusade to protect Constantinople and unify the church under one head. But trouble with Henry IV of Germany caused him to abandon the enterprise. There still dwelt in the minds of the people an ideal monarchy, as represented by the Roman Empire. It was considered the type of all good government, the one expression of the unity of all people. Many dreamed of the return of this empire to its full temporal sway. It was a species of idealism which lived on through the Middle Ages long after the {321} Western Empire had passed into virtual decay. In connection with this idea of a universal empire controlling the whole world was the idea of a universal religion which should unite all religious bodies under one common organization. The centre of this organization was to be the papal authority at Rome. There dwelt then in the minds of all ecclesiastics this common desire for the unity of all religious people in one body regardless of national boundaries. And it must be said that these two ideas had much to do with giving Europe unity of thought and sentiment. Disintegrated as it was, deflected and disturbed by a hundred forces, thoughts of a common religion and of universal empire nevertheless had much to do to harmonize and unify the people of Europe. Hence, it was when Urban II, who had inherited all of the great religious improvements instituted by Gregory VII, preached a crusade to protect Constantinople, on the one hand, and to deliver Jerusalem, on the other, and made enthusiastic inflammatory speeches, that Europe awoke like an electric flash. Peter the Hermit, on the occasion of the first crusade, was employed to travel throughout Europe to arouse enthusiasm in the minds of the people. The crusades so suddenly inaugurated extended over a period of nearly two hundred years, in which all Europe was in a restless condition. The feudal life which had settled down and crystallized all forms of human society throughout Europe had failed to give that variety and excitement which it entertained in former days. Thousands of knights in every nation were longing for the battle-field. Many who thought life at home not worth living, and other thousands of people seeking opportunities for change, sought diversion abroad. All Europe was ready to exclaim "God wills it!" and "On to Jerusalem!" to defend the Holy City against the Turk.