OZAV was established on 10 September 1943 by the occupying German Wehrmacht, as a response to the Allied Armistice with Italy proclaimed two days earlier following the Allied invasion of Italy. It comprised the provinces of Belluno, Bolzano and Trento. The Operational Zone of the Adriatic Littoral, comprising the provinces of Udine, Görz, Trieste, Pula, Rijeka, Kvarner Gulf and Ljubljana, was established on the same day.