During the Cold War (1945-1989) a semi-secret network of 'luchtwachttorens' was erected in the Netherlands to protect the Dutch airspace against airplanes from the Soviet Union. The network consisted of 276 posts across the Netherlands of which 137 occurred on already existing buildings such as windmills and towers. The other 138 were specially build for this purpose. Only 17 of these towers remain today as a reminder of the Cold War in the Netherlands.
The network was designed in 1950 to look out for enemy airplanes that flew to low for ground radar. At that time airplanes were thought to be heard up to a distance of eight kilometers. To cover the entire country, 276 towers were erected at a maximum distance of 16 kilometers. Each tower was staffed 24/7 by two volunteers. The 278 towers were divided by eight groups. Within these groups, a total of 80 sectors were established that contained three towers in a triangle.
Only in 1960 the entire network was fully operational. It proved very difficult to find volunteers. More important, on completion the network was already obsolete because radar technique improved dramatically and propeller airplanes were mostly replaced by jet airplanes that flew at the speed of sound. The network of 'luchtwachttorens' was reduced in 1964 and abolished in 1968. Only one Soviet airplane was spotted in the years that the network was operational. Nico Bick.