Since the time of Genghis Khan, some commanders have been assigned to carry out military activities on behalf of the Mongols west of the Oxus River. It was also not annexed to any dynasty, as the region was not fully captured before Genghis Khan's death. For this reason, the rulers in the region were appointed by The Great Khaganate. But in the time of Mongke Khagan, a large army was assembled to fully capture the region. Some princes from the dynasty of Genghis Khan's sons were brought to the administration of the sent army. Apartfrom these princes, many important commanders also took their place in this army. The princes sent by Mongke Khagan were given a number of tasks. According to the tasks assigned: Some groups that resist Mongol rule in the region must be eliminated. The castle and fortifications must be demolished. In addition, the Baghdad Caliphate should be called upon to be subject to the Mongols. After these missions are completed, the Mongol raids should be moved further and the ground should be prepared for the capture of new territories. These duties, which are seen to be compatible with the activities carried out by princes west of the Oxus River, in a way reveal the reasons why they were sent to the region. However, after the Caliphate of Baghdad was captured by the Mongols, it seems that some princes no longer participated in the expeditions. This is undoubtedly the beginning of a new process that will take place in the region. There are a number of contradictions in the sources between the reasons why Tolui's son Hulagu, one of the princes who came to the region, was sent to the west of the Oxus River and the role he took on afterwards. Some sources say that Hulagu came to the region for administrative purposes when he was sent by Mongke Khagan to the west of the Oxus River. But this story does not fully clarify the reasons for the events that occurred when the historical process was examined. Other sources say that Hulagu came to the region only to pursue military and political goals. According to these sources, it seems that the process that led Hulagu to assume the administration of the region began after the capture of the Caliphate of Baghdad in 1258. After the capture of the caliphate, Hulagu sent an embassy delegation to inform his brother Mongke Khagan of his complaints that the princes in the region were acting on their own. After the delegation appeared before Mongke Khagan and explained the situation, the west of the Oxus River entered a new process in administrative terms. In the beginning of the new process, Mongke Khagan's death in 1259, before his brother to Hulagu administration of the region was effective. Hulagu's strongest opponents, who wanted to take over the administration in this process, were the princes of the Jochi dynasty. However, Hulagu managed to eliminate these dissident princes. Afterwards, with the opportunity of the throne fights for the Great Khaganate, it is seen that Berke, khan of Golden Horde, was also involved in the issue. When the historical documents, which have an important role in illuminating the period, are examined in detail, it is seen that Hulagu emerged at the earliest in 1259-1260 with the claim of khanate in the west of the Oxus River. This date is confirmed by many chronic and numismatic data. As can be seen, Hulagu emerged with an administrative claim in the geography in which he came without any administrative purpose and managed to take over the administration with his successful struggle. Thus, he prepared the ground for both himself and his dynasty to have a say in the regional administration.