In a region of ca 7000 km2, the geoarchaeological survey, carried out by the “Arid Margins of Northern Syria” mission, discovered more than one thousand sites. They were in a rather good condition, and for some of them in an exceptional state of preservation. All placed within their environmental context, they shed new light on the knowledge of the steppe regions for all periods in the history of Syria and the Middle East. This article discusses the period of the Middle Bronze Age, which saw an accentuation of the defensive character of the sites and, above all, the protection of the useful territory. The question of borders and, more broadly, of territorial boundaries in the ancient Orient is one of the subjects often debated and the discoveries made in the Arid Margins area have several times contributed significantly to this debate. Thus, one of the oldest boundaries marked on the ground is the “Very Long Wall” that we connect with the Early Bronze Age IV (Geyer et al. 2010). The kind of fortification of the “Arid Margins” zone in the Middle Bronze Age has a different system of logic. At that time was set up what appears to be a genuine network, relying on a hierarchized system (in terms of distribution and dimensions) of fortresses, forts, towers and small towers. This article describes this system which has only been briefly mentioned in our previous publications. It presents the plans of each type of fortified site, specifies their mode of construction and installation, and places them in their environmental context. Since this system was mainly located within the area we were surveying, it has been possible to define on the ground its implantation modalities and morphological characteristics. The constructions are built on naturally fortified locations or more rarely on artificial embankments and are built mostly with large polygonal basalt blocks. One of the decisive criteria for their location is the visibility between establishments, which are spaced at a maximum of 20.8 km, to allow signals-based communications. According to this logic, we were able to reconstruct the extension of this network well beyond the limits of the zone we have been surveying, on a distance north-south of ca 150 km for an average depth of 30 km (but which can reach more than 70 km). This research, using satellite imagery, has allowed to discover unknown and unpublished sites, some of them reaching up to 50 ha. Finally, the geometrical characteristics of their geographical distribution, too regular to be due to chance, show that there is a unity between this network and the large contemporary cities known around the steppe: Yamhad (Aleppo), Qatna (Tall Mishrifa), Ebla (Tall Mardikh), Tall al-Nasiriya, Tall Tuqan and Tall al-Sour. These largely unpublished data, connected with the context of the settlement of the margins of the steppe during the Middle Bronze Age, allow us to propose a first interpretation of the primary functions of this network. It was established for the most part at the eastern edge of fertile basaltic plateaus, making the most of the relief, decidedly turned towards the east, and its role would consist in the defense of the territory, the surveillance and protection of the axes of circulation (some of which have been stated by our study), communication (by signals), but also and above all the protection of the most attractive lands in terms of potential for settlement and agricultural development. It is at least towards these conclusions that the analysis of the geographical and material data provided by the survey of the arid margins area of Northern Syria leads. Our research, based on the analysis of a corpus of nearly a hundred sites, shows that, from the end of the Middle Bronze Age I, a defense organization would have been set up on a regional scale and as well, most likely, the coordination of the defensive systems of several kingdoms involving an overall design, a concerted project. This structuring would have been based on the creation of new sites, fortifications at the edge of the basaltic plateaus dominating the steppe and their network of secondary installations: forts and towers, which protected the lowlands agglomerations during the Middle Bronze Age II. The findings of the “Arid Margins of Northern Syria” mission thus make it possible to reinterpret the results of the study of the neighboring regions and sites and to consider the whole from a broader and systemic point of view, thanks to a diachronic and multidisciplinary method of survey and global analysis, developed, tested and validated by our team. The purpose of this article is to present to the specialists of this period the primary data collected during the survey of the arid margins and by the study of aerial imagery in an analysis detached from the historical considerations, but which we wanted rigorous. The description of this network is only a first step. While waiting to be able to return to the field, we leave it to the historians and archaeologists specialists of the period to deepen these lines of reflection.