Fort Pannerden was constructed between 1869 and 1871 to serve as part of the New Dutch Waterline. Originally built completely out of brick and mortar, with just one main battery guarding the Rhine, it was upgraded significantly during 1885-1895. The main battery was completely rebuilt, with armour and concrete, while two additional armoured batteries were added and the roof of the fort was reinforced with concrete. The fort had strategic significance in that it guarded the Pannerden Canal, which supplied the water for the inundations of the New Dutch Waterline and could potentially be used as a route towards the main line of defence, but the fort saw little active service.
In World War I the Netherlands remained neutral, although the fort was manned as part of a general mobilisation. In World War II on May 10, 1940, during the German invasion of the Netherlands, the fort was first bypassed and then surrounded. On May 11, cut off from the rest of the Dutch army, the commander of the fort surrendered under threat of artillery bombardment and air attack. Most of the fort was subsequently stripped of all useful materials and after 1945 the building fell into disuse.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.