The mle 1889 was derived from the earlier Mortier de 270 mm modèle 1885 siege mortar and adapted to the coastal artillery role by fitting the same barrel to a different carriage.

[1] The recoil system for the mle 1889 consisted of a U-shaped gun cradle which held the trunnioned barrel and a slightly inclined firing platform with hydraulic buffers.

At the outbreak of the First World War, it is estimated there were 86 mle 1889's deployed in coastal fortifications.

Two sources of heavy artillery suitable for conversion to field use were coastal fortifications and surplus naval guns.

[4] These narrow gauge tracks were also used to re-position the mortars and bring up their ammunition and supplies.