by train, the guns were mounted in October 1935. World War II and postwar Units of the Wehrmacht approached the peninsula on 9 September 1939. Hel, manned by some 2000 Polish soldiers, was the longest-defended pocket of the Polish Army during the whole campaign. Cut off from the mainland on 14 September and shelled with 280 millimeter guns, it surrendered on 1 October 1939 after a fierce defense, during which many German planes were shot down. Some sources, such as Dictionary of Battles and Sieges, put the date of surrender on 2 October 1939. During the German occupation of Poland, Hel, reverting to its German name of Hela, was a major training facility of U-boat crews. Almost immediately after cessation of hostilities, the Germans began further construction work on the base. Among others, the Schleswig-Holstein battery was built for three 40.6 cm SK C/34 guns ("Adolf guns"). These guns fired shells of up to 1030 kilograms, and their range was up to 56 kilometers. Toward the end of the war, the Germans began construction of an airfield, but it was never completed. The Wehrmacht also installed Würzburg-Riese radar stations, as Hela was supposed to defend the main naval port of Gdynia, renamed Gotenhafen. On the night of 3–4 April 1945, the Germans carried out Operation Walpurgisnacht, during which thousands of soldiers and refugees were transported from Gdynia to Hela. The German soldiers on the peninsula repelled several Soviet attacks and surrendered on 14 May 1945, six days after Germany had capitulated. In the Polish People's Republic, Hel did not lose its strategic importance. The peninsula was among the most protected military bases of the country. The base was rebuilt and strengthened, with Soviet-made guns of 130 mm. As time went on, new military doctrine reduced the value of coastal artillery. Because of that, all coastal batteries in Poland were decommissioned. Everything that remained was in 1999 designated as military monuments. Currently Entry to some areas of the Hel Fortified Area is restricted by the military, but most places are open to tourists. Among the most notable monuments are: Laskowski battery number 1 (1935), where in late 1930s, four Bofors 152 mm guns were placed. In 1948, the battery was redone, its name was changed to 13 BAS, and Soviet-made B-13 130 mm naval guns were mounted. One of these guns can still be seen, battery number 21 (1935), where 2