Hegra Fortress is a small mountain fortress built between 1908–1910 as a border fort as a defence against the perceived threat of a Swedish invasion. After the 1905 dissolution of the union between Norway and Sweden, the Norwegian military harboured continued fears of a Swedish invasion to retake Norway.
The fort's guns came from the dismantled Ørje Fortress in Marker. The artillery was made up of flat angle guns with a range of 6 to 9 kilometres. The fortifications themselves consisted of 300 metres of halls and tunnels dynamited into the mountain at Ingstadkleiva, as well as trench systems and gun positions excavated from the rock with explosives. There are two main underground parallel tunnels of around 80 metres length, with a 35-metre tunnel connecting them at a straight angle. One of the main tunnels served as crew quarters while the other was in direct connection with the above ground artillery pits. The fortress' artillery consisted of two 7.5-centimetre and four 10.5-centimetre positional artillery pieces in half-turrets placed in pits dynamited from the rock and lined with concrete, as well as four Krupp M/1887 field guns.
During the period 1910 to 1926 the fort was used as a major military base for the Trøndelag border areas with Sweden. In 1926, Ingstadkleiva Fort was put in reserve as part of the post-World War I defence budget cuts. From 1934–1939, the deactivated fort was used by the Norwegian Red Cross's youth branch as a summer holiday camp for children. In late 1939, Finnish soldiers of the independent Lapland Group who had crossed the Norwegian border into Finnmark escaping the fighting in the Petsamo district in northern Finland were interned at Ingstadkleiva Fort. All the Finns were repatriated during the early days of 1940. During the Finnish internees' stay a sauna was constructed at the fort's camp.
In 1940, from 15 April to 5 May, Hegra was attacked by the German invaders. During the first week the attacks consisted of two infantry assaults; however in the last two weeks attacks mostly featured heavy artillery fire and Luftwaffe bombing, as well as aggressive patrolling. During the siege large portions of the fort were covered in snow, and as all plans of the fort were stored in German-occupied Trondheim several sections of the fortifications were not discovered by the defenders before the 5 May surrender.
After the end of the Second World War, Hegra Fortress was returned to Norwegian control and is today used as a museum with exhibitions detailing the fort's history with an emphasis on the 1940 siege. There is also a café and a souvenir shop. The museum is often used for conferences and for seminars on issues of war and peace. Hegra Fortress is still owned by the Norwegian Defence Force and financed through the Norwegian Ministry of Defence.References:
First record of Kastelholma (or Kastelholm) castle is from the year 1388 in the contract of Queen Margaret I of Denmark, where a large portion of the inheritance of Bo Jonsson Grip was given to the queen. The heyday of the castle was in the 15th and 16th centuries when it was administrated by Danish and Swedish kings and stewards of the realms. Kastelhoma was expanded and enhanced several times.
In the end of 16th century castle was owned by the previous queen Catherine Jagellon (Stenbock), an enemy of the King of Sweden Eric XIV. King Eric conquered Kastelholma in 1599 and all defending officers were taken to Turku and executed. The castle was damaged under the siege and it took 30 years to renovate it.
In 1634 Åland was joined with the County of Åbo and Björneborg and Kastelholma lost its administrative status.