In the present article the author deals — in paralel with major political events — with the hinterland military defence organisation of the Koper commune during the supremacy ofthe Venitian Republic in Istria (13th — 18th centuries) and establishes that from the beginning of written sources on, the Slovenes appeared as carriers of country defence and presented on townboundaries firm ethnic groups with the so-called Captain of Slaves at the head. Village small forts (kaštel or gradeč) presented local defence centres and shelter from hostile, particularly Turkish raids, and at the same time a fortified communal boundary zone.