During the Second World War, a scaffolding was built on the sea wall between the houses Sédyk 4 and 6 and on the Griene Leane under Tzummarum by order of the German occupiers, which was part of German air defense. The 'Ortskommandantur' of the Stelling Koehoal was based in Franeker.
The construction of the scaffolding took place largely in the year 1941. Seen from the direction of Tzummarum, immediately after the house Sédyk 6 on top of the sea dyke was a sentry post with a shelter for the watch at the bottom of the dyke and from the direction of Dijkshoek under Firdgum near the houses. Sédyk 3 and 4 have an identical arrangement. A publication by the then municipality of Barradeel shows that from 30 March 1942 a section of the public road along the seawall, as well as a section of the Griene Leane, was closed. The closure was indicated by signs. About 50 to 70 German soldiers from the Wehrmacht and Luftwaffe were always housed on the position.
The position consisted in total of 4 bunkers, 3 stone buildings, a large wooden barrack, parking lots, sentries, a gun platform for 4 artillery guns on the sea side of the seawall. The entire area was enclosed with a barbed wire fence and land mines. The position was supplied with electricity, water and telephone from the Hare region. The house Sédyk 5, which was located within the barbed wire barrier, was built around 1928 and owned by the couple Pieter Tjeerd Heeringa and his wife Lieuwkje Kroese. This house was claimed by the Germans and the Heeringa couple lived during the war years in the former school house in Firdgum. The Sédyk 5 house was occupied in 1942 by the commander of the Stelling Koehoal.