 The Battle of Frigidus between the army of Eastern Emperor Theodosius I and the army of the Western Roman ruler Eugenius took place in this region in 394.In Medieval Times, the upper eastern part of the valley, including the town of Vipava and half of the town of Ajdovščina, used to belong to the Duchy of Carniola (specifically, to Inner Carniola), while the lower western part was incorporated in the County of Gorizia and Gradisca and thus to the Austrian Littoral.Today, the inhabitants mostly feel part of the "Goriška" region of the Slovenian Littoral, and the Carniolan identity has almost completely disappeared.