The construction and expansion of the border installations had one purpose: they were to prevent people from East Berlin and the GDR from crossing the border to West Berlin. The controls were thus directed inward, against the country’s own population. That distinguished this border security system from others.
Floodlights hung high illuminated the strip of sand that was supposed to reveal the footprints of would-be fugitives. The light poles were painted to mark them as the outermost boundary of the manned area; any border guards crossing this line without advance notice would themselves be suspected of an escape attempt. In front of this “control strip” was a border patrol road for patrol and supply vehicles. Vehicles reached this paved road though gates built into the inner wall. The observation towers that rose behind the border patrol road were another element of the barrier system; these were organized into groups coordinated by one command post. Dog runs or other obstacles were often set up in front of the line formed by the observation towers. In front of the towers and other obstacles was the electrified signal fence that would set off an alarm on contact.
Self-firing devices and mines, used in large sections of the inner-German border between the GDR and the Federal Republic of Germany, were not installed in Berlin.
The first barrier one would encounter on the East Berlin side was the inner wall, into which buildings, firewalls, and factory walls were sometimes integrated. As a result, it was not perceived in East Berlin as a single, uniform structure, despite marking the boundary of a border strip that was between five and several hundred meters wide.
Often other “perimeter defenses” had been installed before this first barrier; then came the “border area,” accessible only with special permission.