main line of resistance

Main Line of Resistance, or MLR is a military term describing 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 enemy advance. MLR first came into use during World War I, after fighting became stalemated across northern France. The French and British on one side, and the Germans on the other, built elaborate fortified defensive positions, characterized by extensive use of barbed wire, entrenchments and underground bunkers, in an attempt to secure their positions, protect their troops from enemy fire, and defeat enemy attacks. The depth of such positions could range from several hundred to several thousand meters, and in a few cases much farther. If the position was held in great depth, a screening line of strongpoints and fortified outposts - designed to slow and disorganize an enemy attack - might be constructed forward of the MLR, and a reserve line built behind it.
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