The origins of the infantry shelters (abris in French) can be traced back before and during the First World War. Abris were the ‘homes’ for the RIF troops, stationed in the intervals between the GO’s and PO’s.
There were two types of infantry shelters. The first one was the abri-carverne (underground infantry shelter): this type of abris could be recognised by two entrance blocs on the surface (appr. 60m apart), while all the dormitories, kitchen, aggregates etc. were underground to provide maximum protection.
The depth at which these abri-carvernes were build varied. When the ground contained rocks, the depth was 8m, while soil containing clay permitted building at a depth of 20m.
The second one was the abri-surface (surface infantry shelter): these huge concrete blocks were largely above ground, and had 2 entrances.
For both types, defence was provided by FM embrasures and two GFM cupolas on top (in the case of an abri-caverne). However, there were (very rare) exceptions, for example an abri with a JM cupola or an anti-tank gun (see text below).
The infantry shelters were equipped with a charcoal-kitchen and sufficient life-supplies for four days.
Furthermore, there was storage room for rations for 15 days. The heating was provided by a boiler providing hot water.
The warmth was spread throughout the dormitories and offices by means of the ventilation system.
The infantry shelters which also served as headquarters, had a radio-room, and could be easily recognised by the horizontal antenna on the outside.
58 abris were build on the ‘old front’ from Aumetz to the Rhine while 25 infantry shelters of a much simpler type were build along the Rhine.
Infantry shelters had a passive role, and were therefore build in area’s which would not bear the brunt of an enemy attack. However, as noted above, there were three exceptions: abri-caverne Petersberg (SF Thionville) had a cupola, ‘abri-surface’ Colming had a firing room (37mm anti-tank gun and a Reibel JM) to provide flanking fire to the right to support casemate d'Éblange and abri-surface de berge du Rhin Leopold was equipped with a JM cupola.
Worth mentioning are two infantry shelters which had different architectural features: abri-surface de Heidenbuckel with a protruding caponier (a casemate protruding from the facade, providing flanking fire) and abri-caverne de Petit-Rederching which had three entrance blocs, instead of two.