The Austro-Hungarian army approached the war as it was a scientific discipline. In the 1880s, when it was decided to strengthen the border towards Montenegro, military engineer Karl Wahlberg designed a special type of mountain two-part fortress made of hewn stone. Such was Petrina, which was originally built as a three-storey defensive barracks. After three years, two semicircular artillery platforms were added, as seen in the plan of Petrina². Like all other fortification facilities designed for accommodation of people, Petrina had its own NN infrastructure (cistern, generator, sewerage) and everything necessary for the life of the army (kitchen, dormitory, common rooms, bathrooms, military medicine). The fortification system meant that all fortresses were optically connected for the purpose of mutual communication, so that at least two to five fortresses could be seen from each other.