Situated halfway between the Zagros mountains and the capitals of Dūr-Kurigalzu and Babylon, the Middle Diyala region (around the present-day Hamrin basin) was actively colonised from the 14th century onwards by the Cassites. Throughout the second half of the 2nd millennium, this region was nevertheless marked by its proximity to Nuzi and a long history of Mittanian influence, followed by the military ambitions of the Middle-Assyrians. The settlement policy pursued by the Cassite leaders had to be compatible with the expression of local identities, in a place of exchange and multicultural settlement that acted as an interface between different political areas. Through the systematic study of a series of cultural and identity markers that I will present, taken from 10 archaeological sites and epigraphic sources from this region, my aim is to illustrate more generally how the Cassite dynasty, a new actor of the international scene, integrates with the economic, political and cultural dynamics of Late Bronze-Early Iron Age Mesopotamia. In fact, this peculiar region, located between the mounts Hamrin and Mirwari, and the Diyala and Nairi rivers, displayed specific features in terms of material culture, architectural choices, as well as settlement and subsistence strategies, that set it apart from the surrounding areas, particularly the Lower Diyala area further south, much closer to the political capitals of Karduniaš. Although apparently peripheral to the baricentre of the Middle-Babylonian state, the settlements in Middle Diyala show a very clear and dense Cassite faciès, which proves the importance given to this geographical area, with an asserted economic dynamism and whose elites mix with, or even copy, Babylonian traditions. At the same time, the archaeological and epigraphic record also reveals a number of heterogeneous cultural and identity markers, which bear witness to several contacts with the Elamite, Mittanian and Assyrian worlds, as well as to local and isolated (indigenous?) practices of micro-production and burial. On the whole, the specifities of Middle Diyala suggest that we should move beyond the concept of “middle-ground” developed by Irad Malkin, in favour of his other concepts of “fusion” or “mixture”, in order to better understand the way in which Cassite identity was inscribed, arranged and interacted with large-scale politics.