'Walpurgisnacht' was the German retreat of the remnants of Generaloberst Walter Weiss’s disbanded Heeresgruppe 'Nord' as well as a large number of German civilians from Gdynia into the Festung 'Oxhöft', as the Hel peninsula, 21.75 miles (35 km) long, was designated (3/4 April 1945).
Soon after Poland gained its independence from Russia in 1918, the Polish military authorities began preparation for the construction of a fortified army garrison along Poland’s Baltic Sea coast, and in 1922 work was completed on a strategic railway line extending from Puck on the south coast of the Bay of Puch, through Władysławowo at the landward end of the Hel peninsula, to Hel at the tip of the peninsula. A telegraph line and a road ran parallel with the railway. In 1931 the Poles started to construct a naval base at 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, and in the mid-1930s work began of major construction projects. A network of rail connections, mostly narrow-gauge, was built, together with concrete-strengthened artillery positions. Armaments and other military equipment were brought in, and work began on the modernisation of the naval base at Hel. An underground power plant was placed some 0.9 miles (1.5 km) north of the port and, in the nearby forest areas, bunkers for ammunition, mines and torpedoes were built. Underground fuel tanks were constructed, with a pipeline to the port. In July 1935 the Poles bought four Bofors 152-mm (6-in) guns, which were mounted in Hel during October 1935.
The battle for Hel was one of the longest battles in the German 'Weiss' (i) defeat of Poland in September 1939. German units approached the peninsula, which had a 2,000-man garrison, on 9 September. Hel was cut off from the mainland on 14 September and, shelled by 280-mm (11-in) guns, and surrendered only on 1 October after a fierce defence, during which many German aircraft were shot down.
During their occupation of Poland, the Germans renamed Hel as Hela, and its naval base became a major training facility for U-boat crews. Almost immediately after cessation of hostilities with Poland, the Germans began work on upgrading the Hela base area with, among others things, the Schleswig-Holstein battery for three 406-mm (16-in) guns. In later stages of the war, the Germans began construction of an airfield, but this was not completed, and also installed a Würzburg-Riese early-warning radar as Hel was deemed part of the outer defences of Gdynia, which the Germans had renamed Gotenhafen.
After 'Walpurgisnacht', the German forces and the civilians they were sheltering held out against the Soviet forces until 9 May 1945, when they surrendered.