CORF interval casemates were build during the different building phases of the Maginot line. Introduced by General Belhague in early 1929, their purpose was to defend the areas and obstacles (barbed wire and anti-tank) between the main components of the Maginot line, the ouvrages, by means of flanking fire. This concept originated from experience during the first world war.
In most cases, CORF interval casemates defended the obstacles placed in between the GO’s and PO’s with machine guns, mortars and anti-tank guns. When you study the casemates, you notice that the firing chambers are not positioned towards an attacking enemy but to the flanks. There were 2 main reasons for this: it minimised the chance of receiving direct frontal fire and second, should attackers pass the casemates, they would be hit in the flanks, a most vulnerable spot.
This illustration shows a general view of two double interval casemates (spaced around 1200m apart) between two ouvrages (not depicted).
In front of the casemates was often a mound of earth (indicated in brown) in order to conceal the embrasures and concrete.
The artillery of the ouvrages and army had to provide fire support when casemates were attacked head-on.
Limited frontal fire support was available by the casemates themselves in the form of FM 24/29’s, JM’s and mortars.