The history of research of the claustra Alpium Iuliarum barrier system is full of interesting stories since individual sections of the barriers attracted the interest of travellers, topographers and other explorers of this area centuries ago.
Medieval written sources tell us that the remains of the barriers served as markings on the terrain, especially for various plot, church and provincial borders or the borders between feudal estates. Individual barriers are also mentioned in various topographical descriptions from the 18th and the beginning of the 19th century, but not as a uniform, interconnected barrier system.
Exploration of Alpine barriers in the 19th century
The first wave of scientific research of the Late Roman barriers began in the mid-19th century. At that time, individual barriers were already understood as a wider military system connected with the roads at the Alpine crossings and dated to ancient times. The curator of the Provincial Museum of Carniola (now the National Museum of Slovenia), Alfons Müllner, endeavoured at the Federal Monuments Authority Austria in Vienna for a systematic research of the barriers and he also created an important archaeological topographic map of the Ajdovski zid wall and examined the topography of the barrier on the Hrušica Plateau and some smaller excavations. Thanks to his work, other researchers who were involved in the study of Roman remains in the area of the Alpine barriers began to include the Late Roman barrier system in their work.
One of the first to write about the barrier system was Alberto Puschi, the director of the Trieste Museum. In 1901, in a retrospective text on the Alpine barriers, he was the first to write that, contrary to the established belief, this was not a continuous line of walls, but individual barriers. The text is also equipped with a map, which, despite the errors, remains one of the basic topographic sources for studying the barrier system.
The 1st wave of exploration of Alpine barriers in the 20th century
The first systematic archaeological excavation on the Alpine barriers took place in 1906 in Vrhnika. It was not until the First World War that larger excavations under the leadership of Walter Schmid, a provincial archaeologist at the University of Graz, began in the wider area of the barrier system. Unfortunately, with the exception of two shorter texts, the results were not published.
Both wars and the interim economic crisis almost completely interrupted the exploration of the barrier system. The exception was the conservation work on the Ad Pirum fort (Hrušica) and the barrier in Rijeka between 1937 and 1940. At that time, unfortunately, the Alpine barriers were also used for political purposes; the Italians searched for arguments for the course of their north-eastern border and used them in the Rapallo Treaty, which also established the border between the Kingdom of Italy and the Kingdom of Yugoslavia. To this end, the Italian army was secretly carrying out topographical inspections and smaller excavations in the area of the Late Roman barriers, which probably do not have greater scientific value.
The 2nd wave of exploration of Alpine barriers in the 20th century
In the middle of the 20th century, a second large wave of exploration of the claustra Alpium Iuliarum barrier system began. On the initiative of the archaeologist Jaroslav Šašel, a team of Slovenian and Croatian archaeologists created the entire topography of the barriers and collected all related publications and ancient sources. Thus, in 1971, the monograph claustra Alpium Iuliarum I was published, containing the first systematically collected and evaluated material, which is nowadays still considered the basic work on the barrier system.
With his professional and visionary approach to the study of Alpine barriers, Jaroslav Šašel attracted numerous big names of the then Yugoslav archaeology. They included Peter Petru (Institute for Monument Protection of the Socialist Republic of Slovenia), Radmila Matejčić (Maritime and History Museum Rijeka), Mehtilda Urleb (Notranjska Museum Postojna), France Leben (Karst Research Institute Postojna, SAZU), Mitja Brodar and Stanislav Jesse (both SAZU). Their dedicated work yielded results since systematic archaeological excavations of the Alpine barriers took place simultaneously until the beginning of the 1980s.
The 3rd wave of exploration of Alpine barriers in the 20th century
Also in the last two decades of the 20th century, the exploration of the claustra Alpium Iuliarum barrier system continued, but to a slightly smaller extent than before. The research was conducted on the ancient fortified cities of Tarsatica (today’s Rijeka), Castra (today’s Ajdovščina) and Nauportus (today’s Vrhnika) and on the fortlets Gradina above Pasjak, Brst near Martinj Hrib and Lanišče. The archaeological excavations at Lanišče took place between 1961 and 1963 and the fortlet was then also reconstructed. Today, it is the largest reconstruction in the Late Roman barrier system. At the Ad Pirum fort in Hrušica, the international Slovenian-German archaeological team excavated in the years 1971 – 1973, led by Peter Petru from the National Museum of Ljubljana and Thil Ulbert from the University of Munich. The National Museum continued the excavations with its team on the site until 1979. Parts of the barrier walls in Jelenje, Studena, Prezid, Benete, Rakitna, Ajdovski zid and the barrier walls along the Ad Pirum fort were also explored.
Exploration of Alpine barriers today
Unfortunately, by the end of the 1980s, systematic research of Alpine barriers was reduced. Nevertheless, it is necessary to highlight the efforts of individuals who continued to contribute significantly to a better understanding of the barrier system by researching archaeological material or topographic work. The Slovenian researchers included Nada Osmuk, Drago Svoljšak, Jana Horvat, Slavko Ciglenečki, Veronika Pflaum, Verena Vidrih Perko and Marko Frelih. In particular, it is necessary to mention the topographical and research work by Peter Kos and Jure Kusetič, who have been most intensely dealing with the entire system of claustra Alpium Iuliarum in the recent years and have also been publishing their results.
In the framework of the Croatian archaeological research of Alpine barriers, the systematic archaeological excavations of the alleged building of the military command in Rijeka in 2007 should be highlighted, which were also appropriately published. Among the Croatian researchers, Ranko Šarac (Maritime and History Museum Rijeka) and Josip Višnjić (Croatian Restoration Institute) are today mostly dealing with the exploration of the barrier system, which also includes archaeological excavations of individual barriers in Croatia.