Until the late 1960s, the fortifications were constructed almost up to the actual border line. When the third-generation fortifications were constructed, the fences were moved back from between 20 metres (66 ft) to as much as 2 kilometres (1.2 mi). This gave the guards a clear field of fire to target escapees without shots landing in the West and provided a buffer zone where engineers could work on maintaining the outward face of the fence in East German territory.