In 1932 the Afsluitdijk was closed. This meant a new military threat to inner Holland, a fast route to Amsterdam. The army demanded a thorough defenceline with money from the Water department. This resulted in a total of four defencelines, two on each end of the dike, with impressive bunkers, the strongest of its kind in Holland at the time. Kornwerderzand was the only place where the Germans did not get through the Dutch lines in 1940. After the war of May 1940 the Germans took over the defences and added three heavy bunkers (1 x 612 and 2 x 667), brick daytime quarters, one man pits, trenches and anti-tank obstacles including a Walzkörpersperre. The Dutch bunkers were converted to German standards including gasfilters. This became Widerstandsnest 27aH which was occupied by the Deich Kompanie with 4 lowrank officers and 39 men. Another lowrank officer and 12 men of the Grenz Aufsicht Stelle (Border patrol) made the crew complete. A total of 4 light Mgs, 2 heavy Mgs, 2 x 5 cm KwK and a Yugoslavian 7.65 cm LAG defended the Wn.
One of two German 667 anti-tank gun bunkers with the 5cm KwK still present.