"Defense line" is actually a traditional and somewhat simplistic concept.
A defense line is not a single line but rather a strip-like area. Modern warfare's defense lines are not continuous but assembled from numerous fortifications.
The sturdiness of these fortifications and the density of deployment are determined by military needs and battlefield conditions.
The barbed wire and trenches common to traditional defense lines have nearly vanished in modern warfare.
The main structure of a defense line is in fact a scattering of foxholes, interspersed with fortified firepower points reinforced with sandbags and sleepers.
Compared to previous wars, especially during the First Global War, today's defense lines are considered very rudimentary.
However, for modern warfare that has achieved electronic automation and is about to enter the information age, fixed defense lines are not the decisive factor for victory.
