The expression oikoi stratiōtikoi , used in Constantine VII Porphyrogenitus as opposed to oikoi politikoi , designates all those families who were bound to military service. They, in the tenth century, were listed in various enlistment registers that were periodically updated, among which one was kept in Constantinople. There is solid evidence to argue that such an administrative practice originated in the eighth century, coinciding with a significant transformation in the enrolment of soldiers and their maintenance. A conscription procedure was devised in the age of the Isaurians, which, although it is not known whether it was on a voluntary or compulsory basis, entailed the entry in the military records (in Constantinople and the provinces) of every person in charge ( oikodespotēs ) of the family that had assumed the military burden. This implied in later periods a strong uncertainty in the relationship between service and its performance because registration rested on an ambiguous vocabulary. The ambiguity, in fact, was rooted in the polysemy of the concept of oikos , family unit, home and patrimony at the same time. While such a notion allowed the recruitment in thematic armies to function flexibly through the wide network of the family’s cognate and agnatic structure, precisely because the oikos was also a set of economic interests, it exposed the landed patrimony of military families to splitting and erosion. This ambiguity ended with Constantine VII’s famous law of 949, which regulated the property regime of the stratiōtikoi oikoi , a regime that, as the same provision explicitly states in several points, already existed previously throughout the empire. The law provided a precise economic quantification of the assets needed for each ‘military family’ to perform the service. Historiography has generally interpreted Constantine VII’s measure as an act breaking with the previous tradition, since military service appears in it much more markedly connoted as a patrimonial burden, rather than as a personal one. However, this ‘oppositional’ interpretation does not seem adequate for understanding the concept of oikos stratiōtikos , which from the outset must have implied a profound interrelationship between the personality of the service and its patrimonial basis, since the one did not exist without the other.