The Fourth Crusade is an extremely complicated historical phenomenon in which the most various interests and emotions are reflected; lofty religious emotion, hope of reward in the life to come, craving for spiritual action, and devotion to the obligations which had been undertaken in behalf of the crusade were mingled with the desire for adventure and gain, inclination for traveling, and the feudal custom of spending life in war. The domination of material interests and worldly feelings over spiritual and religious emotions, which had already been felt in previous crusades, was particularly evident in the Fourth Crusade; this was demonstrated in the taking of Constantinople by the crusaders in 1204 and the foundation of the Latin Empire.
At the end of the twelfth century, and especially in the epoch of Henry VI, the German influence was preponderant in Italy, and Henry's eastern plans threatened danger to the Eastern Empire. After his sudden death circumstances changed. The new pope elected in 1198, the famous Innocent III, turned his attention to restoring in full the papal authority, which had been undermined by the policy of the German sovereigns, and to putting himself at the head of the Christian movement against Islam. Italy stood on the side of the pope in his struggle with the German influence. Seeing the chief foe of the papacy and Italy in the Hohenstaufens, the pope began to support in Germany Otto of Brunswick, elected king by a portion of Germany against Philip Hohenstaufen of Swabia, brother of the late Henry VI. A very good opportunity seemed presented to the Byzantine Empire to carry out the plans of the Comneni to replace the German world state by a similar Byzantine world state. With this in mind, probably, the Emperor Alexius III wrote Innocent III in the year of the latter's election to the papal throne: We are the only two world powers: the single Roman Church and the single Empire of the successors of Justinian; therefore we must unite and endeavor to prevent a new increase in the power of the western emperor, our rival. In reality, the complicated situation of Byzantium, both external and internal, left no hope for the success of such ambitious plans.
Cf. Venetians and Crusaders take Constantinople (1204) - Plunder of the Sacred Relics, by E. Pears
A History of the Byzantine Empire - Table of Contents
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