Main line of resistance

A main line of resistance (MLR) is the most important defensive position of an army facing an opposing force over an extended front.

It does not consist of one trench or line of pillboxes, but rather a system, of varying degrees of complexity, of fighting positions and obstacles to slow enemy advances.

On 1 December 1916, the German General Staff (Oberste Heeresleitung or OHL) published The Principles of Command in the Defensive Battle in Position Warfare, by two general staff officers, Hermann Geyer and Max Bauer, which described the principles of an elastic defense in depth.

The lightly held outpost zone was there to provide warnings of attacks and repel enemy raids and patrols.

Although this restricted the range of the defensive weapons, this was offset by the advantage of concealment, and the ability to surprise an attacker.