After the Treaty of Karlowitz, the entire city of Arad was on the border region of the Habsburg Empire and so, of critical importance for the Viennese Court as it became a focal point of the Military Frontier administration until 1751.The strategic placement of the city determined Prince Eugene of Savoy, to rebuild and improve the former rectangular Turkish built fortress, on the right bank of the river, but after consultations with the Empress, the decision was made not to rebuild the old fortress, but to erect a new and vastly improved fortified complex on the peninsula lying just south of the city.The project was made after the plans of the Austrian general and architect Ferdinand Philipp von Harsch [de], having the form of a star with six corners, built with three rows of underground pillboxes and several trenches, which in the past could have been flooded.The most famous prisoner in the fortress of Arad was undoubtedly Gavrilo Princip, who on 28 June 1914 killed the heir to the throne of Austria-Hungary, Archduke Franz Ferdinand and his wife, Sophie, in Sarajevo, an event which led to the outbreak of World War I.In an interpellation to the Hungarian parliament in Budapest during 1917, Ștefan Cicio Pop, deputy of the Romanian National Party, warned about the inhumane conditions in which prisoners were held in the fortress of Arad.