In 1204 Innocent's crusade had spiralled out of control, first attacking the Christian city of Zara before adopting the young "rightful" emperor Alexius' cause, and turning ominously towards the capital of eastern orthodox Christianity. There are two main arguments for how this tragic turn of events came to happen. Bartlett argues towards the intrigue theory which is the corruption of a group or groups of individuals which steered the crusade off course towards the tempting prospect of Constantinople. Queller counters this idea, arguing that sack came as the unfortunate result of a series of fateful occurrences.
It has been argued that the signing of the "extortionate" terms imposed by the Venetians in the treaty of Venice was the point at which the crusade became doomed to attack Constantinople; the naive western diplomats conned into signing an agreement which would place them in the pocket and at the mercy of the scurrilous Doge [24]. However, the problematic issue of the treaty was not the projected cost per unit, which was quite modest by contemporary standards [12], but in the severe over-estimation of the number of Crusaders. Interestingly Villehardouin gives no record of any estimation from delegates' behalf of the number of crusaders who would require transport, however, such an omission, coming from the senior envoy of the expedition highlights the embarrassing overestimation of the Frankish envoys rather than any underhand actions by the Venetians.
It is not believable that the envoys had failed to receive such an estimation from the magnates of the crusade at Compienge or that they would have failed to convey it to the Doge. Moreover, it would have been impossible to have opened negotiations with the Venetians for a fleet of an unspecified size. Queller points out that the treaty contracted by Phillip Augustus with the Genoese in 1190 would have charged only half a mark less per unit of one Knight, two Horses and two Squires for a year's transportation than the Treaty of Venice and whilst with the Genoese treaty wine was only to be provided for four months, and the performance of the contract was a continuing source of complaint to the French; sources on the Fourth Crusade have only praise for the fleet prepared by Venice [13]. Any fault one can find in the treaty comes consequently as a result of the gross estimation of the Franks rather than any devious actions by the Venetians as suggested by Bartlett.
Another popular interpretation of the events of the Fourth Crusade is the notion of a conspiracy between Philip of Swabia, Boniface and the young Alexius plotted at Philip's court in the Christmas of 1202 as outlined by Bartlett [21]. The anonymous writer of the Gesta Innocentii exclusively attributes the diversion to such an agreement. However, this was written by some-one who as a supporter of the Pope wished to portray Innocent in the best possible light. The fact that he goes on to absolve Innocent of all responsibility for the events of the Crusade alone should make us cautious of his account. Central to this conspiracy theory is timing of Alexius' visit to his uncle over which there is a division represented in both the primary and secondary sources related to the issue. Villehardouin places Alexius in Italy only a short while before the crusade diverted to Zara from where he was called to present his case to the leaders on Zara. The decision to ask Alexius to come and meet the crusaders was therefore prepared at Zara ergo the diversion began there. Contrary to this Robert of Clari claims that during the discussions at Zara Boniface of Monferrat mentioned he had seen the pretender "last Christmas" while at Philip's court [20].
Byzantine historian Henri Grigoire points out that in his letter to Alexius III, Innocent commented that young Alexius had visited him "formerly", when he could have employed the adverb 'recently'[21]. This implies that the audience with the Pope had taken some time before the letter was written lending support to Clari's account. Unfortunately it is one thing to say that Alexius arrived in Germany in 1202, it is quite another to prove that such a plot took place between Philip, Boniface and the Pretender. Prior to the crusade Boniface seems top have spent a lot of time with men who, although undoubtedly important would not actually be with the Crusade. If he had truly wanted to alter the course of the crusade it seems far more probable that he would have best spent his time negotiating with men such as Baldwin of Flanders and Dandalo. Furthermore, while there is no doubt that Philip of Swabia was a natural supporter of the young Alexius claim due to his marriage connection it would seem that Philip as Bartlett argues “had far too many problems of his own to lend anything above nominal support to Alexius” [22].
