340mm/45 Modèle 1912 gun

The 340mm/45 Modèle 1912 gun (13.4 in) was a heavy naval gun of the French Navy. While the calibres of the naval guns of the French Navy were usually very close to those of their British counterparts, the calibre of 340 mm is specific to the French Navy.

The built-up gun was designed to be carried by the Normandie-class battleship and Lyon-class battleship classes in quadruple gun turrets, but no ship of these types was completed as a battleship. They were carried by the Bretagne-class battleships in twin turrets. Some of these guns were used as railway guns and coastal artillery in World War I, also serving in World War II.

Railway gun
Due to the cancellation or conversion of most of the ships these guns were made for, the relatively large number of spare guns available facilitated their use as railway guns in both World Wars. Two batteries of 340 mm guns, with an authorized strength of one gun per battery, were operated by the 53rd Coast Artillery, U. S. Army, in World War I. As with most French railway guns, after the Fall of France in World War II some of these weapons were used by the German army.

Two different railway guns were produced from these surplus guns:
 * Canon de 340 modèle 1912 à berceau - Six were converted by the St. Chamond company and saw action during both wars.
 * Canon de 340 modèle 1912 à glissement - Six were converted by the Schneider company and these came too late for the First World War but participated in the Second World War.

Coast Defense Gun
During Operation Dragoon, the Free French battleship FRENCH BATTLESHIP Lorraine was one of the units engaged with 'Big Willie', ex-French turret battery controlling the approaches to Toulon. 'Big Willie' was armed with the guns taken from the French battleship FRENCH BATTLESHIP Provence, as a replacement for the original guns, sabotaged by its French crews, making this an unusual instance of both sides of an engagement using the 340mm/45 Modèle 1912 gun.

Weapons of comparable role, performance and era

 * BL 13.5 inch Mk V naval gun British equivalent
 * 14"/45 caliber gun US Navy equivalent