Summary/Abstract: The military leadership of the Kingdom of Yugoslavia was forced to consider border fortifications where it shared boundaries with hostile neighbors. The aim of fortifications was to prevent strategic surprise by the enemy and provide protection for the mobilization and concentration of friendly troops. The first steps towards achieving this goal were made in 1935, when the Standing Commission for fortification, responsible for making a study and project works regarding strategic-geographical and tacticalfortifications, was established. Besides the Standing Commission, the Command for Fortification (with its headquarters based in Ljubljana, with sixteen territorial departments for fortification responsible for the execution of the work on the ground), was established in 1937 to achieve that goal. The first field works began in the spring of 1938 at the western border with Italy. The following year (1939), works started along the northern border, first with Germany (Austria), and then Hungary. Works on the borders with Romania and Albania began in the same year. Yugoslavia began fortifying its eastern border with Bulgaria in the late autumn of 1940. That year works on establishing a Yugoslav marine front also began. By the beginning of the 1941 April War, fortifications had not yet been completed. The border with Italy was the best fortified, and the worst border fortification was with Bulgaria, which would prove crucial in the April War, when the enemy made its first and most powerful attack across it. Completed fortifications were partially occupied by troops called ”Posadne trupe” formed specially for that purpose in the period 1939-1941. The challenge of fortification was often the reason for disputes among the Yugoslav military leadership, because there were those who felt that the money spent on border fortification could have been better spent by purchasing new military equipment and on the readiness of the troops. The results of Yugoslav fortification were far from what was expected. The most fortified parts of the front did not even have the wartime temptation and the ”Posadne trupe” retreated from them without a fight, permitting the enemy to occupy important objectives with minimal effort.
