The Maginot Line - A misunderstood history

Cupola JM Model 1930

Machinegun cupola

This cupola with one embrasure could provide either frontal or flanking fire. It was equipped with the same 7.5 mm machine guns (JM Reibel) as the ones mounted in the casemates and ouvrages.

This design triggered the creative thinking of the CORF engineers. It changed the way the casemates looked after 1930 and increased their field of fire.

A a modified JM cupola A small number of JM cupolas were modified in the field to house an AM armament. It was a labour intensive and technically difficult undertaking.
It was deemed necessary because of the fact that some casemates did not have anti-tank weapons. Work commenced in march 1940.

  Height Outer ø Armour Weight
(petit modèle)
1.70 m 1.60 m 0.20 m 11t/12t
(grand modèle)
2.70 m 1.80 m 0.30 m 28.5t
GM modular 1.95 m 1.75 m 0.27 m 17.0t

The cupola had a mobile platform, and a lift to facilitate the transportation of magazines to the loader.

JM cupolas had a single firing port, which were flanked on either side by trapezoidal observation ports.

The rear was often encased in a concrete embankment, which provided additional cover and reduced the silhouette of the cloche. This in stark contrast to the GFM cupolas of type A and B, which could often be seen from quite a distance.

JM cupolas were used as independent firing positions (in case of ‘casemates cuirassees’), or could be integrated with other weapon positions to create a broader field of fire.
Casemate Cheniere-Est Sometimes it even replaced a weapon in a firing chamber, thus reducing the two main concrete embrasures to 1 instead of 2.