The Hel Fortified Area () was a set of Polish fortifications, constructed on the Hel Peninsula in northern Poland, in close proximity to the interwar border of Poland and the Third Reich. It was created in 1936, upon a decree of President Ignacy Mościcki. It covered most part of the peninsula, and during Polish September Campaign, it was the last place of Poland to surrender to the invading Wehrmacht (for more information, see Battle of Hel). During World War II, the naval base in Hel was used as a major training facility for U-boat crews. History After Poland regained independence in autumn 1918, and the symbolic wedding ceremony with the Baltic Sea by units of the Polish Army under General Józef Haller de Hallenburg (Puck, 10 February 1920), Polish military authorities began preparations of a fortified army garrison along the coast. As early as 22 July 1920 General Kazimierz Sosnkowski ordered construction of a strategic rail line which ran from Puck, through Wladyslawowo, to Hel. The line was completed in 1921, together with telegraph connection, by the logistics units of the Polish Army. A road was constructed along the line. In 1931, Polish Army began the construction of the naval base in Hel. At the same time, the tip of the peninsula, from Jurata to Hel, was placed under military administration. Construction of new houses and tourist facilities was forbidden, movement of civilians was strictly limited. These regulations were strengthened by the decree of President Ignacy Mościcki, signed on 21 August 1936, which officially created the Hel Fortified Area. Soon afterwards large-scale works began. A network of rail connections, mostly narrow-gauge, was built, together with concrete-strengthened artillery positions. Armaments and military equipment were brought. The Army started modernization of the naval base at Hel. The base, designed by Wlodzimierz Szawernowski, had been built in 1931, by a Polish-French Enterprise in a location known as Stary Hel (Old Hel). An underground power plant was placed some 1.5 kilometers north of the port, also in adjacent forests, shelters for ammunition, mines and torpedoes were built. An underground petroleum storage reservoir was constructed, with a pipeline to the port. Even though the Hel Fortified Area was not officially created until 1936, Polish Army had been purchasing equipment for it earlier. In July 1935, four Swedish-made Bofors guns (152 mm) were bought and brought to Gdynia aboard transport ship ORP Wilia. Transported to Hel