укрепрайон(He showed me pictures of the fortifications of Kyiv in 1941. It had been an ukreprayon, a fortified district; an elaborate set of defences were built on its landward side at the turn of the 1920s and 1930s – by James MeekTamerlane)
укреплённый район(A fortified district or fortified region in the military terminology of the Soviet Union, is a territory within which a complex system of defense fortifications was engineered. wikipedia.org'More)
