The three designs varied slightly between each other: Mark I appeared in March of 1916 and sported a shorter barrel that its sister designs while mounting its recuperator / run-out cylinder above the barrel assembly. The Mark III followed by being given a heavier-duty breech section to contend with the inherently violent forces at play as well as to improve the weapon's basic balancing. In July of 1917, the Mark V arrived which relocated the recuperator to just under the barrel for a more natural arrangement and the breech was lightened. To offset this, an integral crew platform was added which rotating with the gun platform - offering 120-degree traversal. BL 12-inch railway howitzers were operated by members of the Royal Garrison Artillery for the duration of the war - which ended with the Armistice of November 1918. After the war many were give up for the scrap heap.
Their formal British Army designation was "Ordnance BL 12 inch Howitzer on Truck, Railway". A towed version also existed and is detailed in a separate entry on this site.
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