Atlı-göçebe bozkır kültürüne mensup Türkler komşuları olan yerleşik kültürlere karşı askeri bir üstünlük sağlamışlardır. Türk akınları önce Çin ve daha sonraları İran topraklarına yönelmiştir. Çinliler bu akınları durdurabilmek için ünlü Çin seddini inşa etmişlerdir. Tarihte İran-Turan mücadeleleri mitolojik dönemlerden itibaren görülmektedir. Farslar da Hazar Denizi’nin güneydoğusundan ve Kafkasya’dan gelen bu saldırılara karşı çeşitli savunma tedbirlerine başvurmuşlardır. Bu amaçla Kafkasya ve Hazar kıyılarındaki geçitlere ve Gürgan bölgesine kaleler, savunma duvarları ve istihkâmlar inşa etmişlerdir. Gürgan bölgesi bozkır sınırında yer alan saldırıya açık bir ovadır. Ayrıca tarihi İpek yolu buradan geçmektedir. Farslar bu ovanın kuzeyindeki bozkırlardan gelen Türk akınlarına karşı Gürgan seddini inşa etmişlerdir. Bu sed yaygın olarak Sedd-i İskender adıyla bilinmektedir. Seddin yapılış tarihi kesin olarak tespit edilememiştir. Kaynaklarda Sasani hükümdarlarından I. Firuz veya I. Hüsrev Anuşirvan zamanında inşa edildiği yer almaktadır. Akhunlar bu dönemde Sasanilerin için büyük bir tehlike haline gelmişlerdir. 1970’li yıllardan itibaren İranlılar ve Batılılar bu sedle ilgili kapsamlı çalışmalar yapmışlardır. Türkiye’de ise bu konuya dair müstakil bir yayın yapılmamıştır.

In history, great defensive walls have been built by the sedentary cultures with an objective to defend themselves against the attacks of horse-nomadic culture. The Chinese, who are exposed to the attacks of Turks, have built the famous Great Wall of China to defend themselves. Another important sedentary culture is Iran that Turks attacked from the south. These attacks which could be traced back to mythological period were carried out from the east and west of the Caspian Sea. Persians Dynasties have always resorted to a variety of defensive measures against these attacks in this two regions throughout the history. At the beginning, they have built castles and fortifications, seeing that they are insufficient, they have build great defensive walls. Gorgan and Tammisha walls have been built in the Gorgan plain at the south and southeast of the Caspian for that purpose. The ‘Great Wall of Gorgan’ also, incorrectly, known as ‘Alexander’s Wall’, runs from the southeast corner of the Caspian Sea for at least 195 km eastwards, into the Elburz Mountains. Its western terminal was flooded by the rising waters of the Caspian Sea, while to the east it runs into the mountainous landscape of the Elburz Mountains. It is, to our knowledge, the longest ancient barrier between the Hungarian Plain and China. The scale of the Wall of Gorgan compares also favourably with that of the most elaborate ancient barriers in Europe. Contrary to earlier hypotheses, it was not built period of the Parthians, let alone the Macedonian king Alexander. Recent scientific dating places its construction firmly in the fifth or, possibly, early sixth century CE, a period when the Sasanian Empire was involved in frequent armed conflicts with the Hephthalites. In this study sought to answer the question that, when this wall was built and for what reason, whether Gorgan and Tammisha walls were two separate walls or not and how extensions of the wall within the sea were built. Fertile Gorgan plain has been a significant region in terms of political, military and commercial sense throughout the history. It has been known that there are numbers of cities and castles are built since ancient times. The most important historical artifact in the region is Gorgan wall. In Turkey, there has not been any independent study or publication on that issue. Persian and English scientists have done extensive work about this wall. However, there are some questions left unanswered that when this wall was built and for what reason, whether Gorgan and Tammisha walls were two separate walls or not and how extensions of the wall within the sea were built. While examining these questions, the geography and history of Gorgan should primarily be considered. Historical names of the wall should be analysed in terms of oral tradition. It is required to evaluate the information in the historical sources in consideration of Turkish-Persian struggles entirely occurred around the Caspian in history. There is significant information about the wall and building of the section within the sea in the Arab-Persian sources particularly in the middle age. The results of the comprehensive surface, archeologic and underwater researches conducted as of 2005 should be evaluated in the light of this information. Various Turkish tribes have always lived and raided to this region in the north of this wall throughout the history. The construction date of this wall dates back to I. Firuz time, ruler of Sassanid, who was defeated against the Hephthalites. It is understood from the archaeological examinations that the wall of Gorgan was built in a fast fashion. Persian names of the wall (Sedd-i Firuz, Sedd-i Anuşirvan), information in the middle age sources and recent archaeological tests have verified this opinion. It is understood that this wall is constructed at the time of I. Firuz as a result of attacks of Hephthalites and some reparations and additions have been made to the wall at the time of I. Husrev Anuş