In the years before the outbreak of World War I positions are fortified on Veli and Mali Brijun, as well as Barbariga. New, more sophisticated forts are built and new long-range artillery is installed at mayor coastal forts. The defense level of the channel is increased to a maximum, which also proves the importance of the channel. At the beginning of World War I, in the entire local waters of Pula a barrier with altogether 1450 underwater mines was set up. Apart from the laid minefields, to the north and south the Fažana Channel was protected by a wire barrier and anti-submarine obstacles. The Fažana Channel that provides perfect protection from both enemies and winds becomes the home of submarines and hydroplanes.
At the beginning of the war, the submarine squadron from Pula harbor is transferred to the island of Veli Brijun. In 1917 the operational submarines return to Pula harbor, whereas the school for submariners operates on Brijuni until the end of the war. As early as 1912 K.u.k. Kriegsmarine buys the seaside establishment “Valbandon” and Kozada Island where it sets up a school for hydroplane pilots. In the Fažana Channel, in the area of Puntižela a new naval hydroplane base is constructed and opened in 1915. Puntižela becomes the new operational naval air force base, and the old one on Sv. Katarina Island becomes an air force arsenal.
Even after the war, the Italian army guards the seized military equipment at Puntižela until 1922, after which it becomes the training base of the Italian naval aviation.