To protect the entry to the important port city of Trieste, by the end of 1943 the German Navy had installed four Italian 90 mm. guns, located strategically south of the city. These guns had a range of 12 km. and could be used against both ships and aircraft. The guns were set in open ring positions cast in concrete.
Istria had been Italian since 1920 and following Italy's surrender to the Allies in 1943, the Germans took over its defence.
The waters around Istria were important to the Germans, especially because of the many small ports along that section of coast from which German supply vessels could sail.
The remains of the gun battery are now scattered around the fields of the Debeli Rtič nature reserve.