The Islamic conquests, which started under the leadership of the Prophet Muhammad (pbuh), have been continued throughout history with the efforts of the Companions and other Muslims later on. The military campaigns carried out by the Islamic army could result in conquest as well as defeats. Internal and external factors had a decisive position in obtaining these results. As a result of the conquests that continued from the time of the Rashidun Caliphate, many regions and cities came under the rule of Islam in a short time. One exception was the Taberistan region on the southern shores of the Caspian Sea. The region, which has a harsh and difficult geography surrounded by steep mountains, was ruled by local dynasties during the Sassanid period. The existence of many dynasties, with the convenience of the topography, also allowed the region to act independently from the political point of view. Gavbare was the most important of these dynasties and continued to exist in the region after the fall of the Sassanids. Due to its topography and political structure, the region had been a shelter for those who belonged to opposition movements during the Sassanid period. This geopolitical situation of the region continued in the post-Islamic period. Although each geography, where the wars of conquest were carried out, had its own advantages and disadvantages, Tabaristan, in the conquest movements of the Muslims, was one of the regions where the furthest difficulties were experienced due to its both topography and human nature. The fact that the region could not be fully conquered for a long time and the problems experienced in this process require the subject to be examined from a different perspective. For this purpose, in the first part of the study, information about the naming and geography of the Taberistan region takes place. In the second part, the military campaigns to the region were handled chronologically. In the third part, the problems experienced during the conquest process were evaluated that lasted for about two centuries. Geographic conditions and climate were the most important factors that the Islamic conquests could not be permanent in the region. The rainy climate and the muddy terrain resulting from it, that Muslims were unaccustomed to, and the montainous terrain were the main promlems. In addition to the difficulty of the geographical conditions, Muslims who were foreign to the region, suffered serious defeats by falling in various war traps. Another reason for the failure was the negative consequences of some decisions taken by the Muslim commanders. The fact that the people of the region had a warlike character was one of the reasons for their long struggle with the Muslims. Long-term conflicts, which also had devastating consequences for Muslims, resulted in agreements made at various times. Despite the agreements made, it is seen that the people of Taberistan break the agreements whenever they find the opportunity. Additionaly, local administrators organized the people of the region and led various rebellions. Failure to comply with the agreements and the rebellions caused military campaigns over the region. The organization of these military campaigns were not easy, the distance of the region and the problems experienced in the settlement of Muslims to the region created problems in terms of logistics. When the conflicts between the Muslims were added over all the problems, the seizure of the region by the Muslims spread over a long period of time. These problems identified in the study aimed to look at the Islamic conquests from different perspectives and to present an example of analysis at the regional level.