The Armstrong Whitworth 12-inch naval gun of 40 calibres length was designed by and manufactured mainly by Armstrong's ordnance branch, Elswick Ordnance Company. It was intended for the Royal Navy's s, but budgetary constraints delayed their introduction. The first units were instead supplied to Japan. As the Type 41 12-inch 40-calibre naval gun it was the standard main battery on several early United Kingdom-built pre-dreadnought battleships of the Imperial Japanese Navy. It later entered service with the RN as the 12-inch Mark IX, being fitted to warships of three pre-dreadnought classes prior to World War I. Also, during the war several guns were converted for use as railway guns, and, towards the end of the conflict, for use on the M-class submarine monitors. The gun also saw service with the Italian Regia Marina, in two classes of pre-dreadnought battleships.
Design and development
The Type 41 12-inch naval gun was produced by Armstrong Whitworth, Elswick, Newcastle upon Tyne, as a slightly modified version of the "EOC G pattern" 12-inch guns used on contemporary Royal Navy battleships.
Japanese service
Japan purchased a total of 44 of these weapons for use on the four ships of the and, and the battleships and. Each ship carried four guns in twin turrets. In combat at the Battle of the Yellow Sea in the Russo-Japanese War, Japanese battleships Asahi, and Mikasa all had one of their main guns taken out of action due to premature bore detonations. The cause was traced to faulty fuses, and the problem was rectified prior to the Battle of Tsushima. The gun was officially designated as "Type 41" from the 41st year of the reign of Emperor Meiji on 25 December 1908. It was further re-designated in centimetres on 5 October 1917 as part of the standardization process for the Imperial Japanese Navy to the metric system. The Type 41 12-inch gun fired an shell, with either an armour-piercing, high-explosive or general-purpose warhead.
Armstrongs also sold versions of their 12-inch 40-calibre gun to Italy to arm the two and the four s. The version for the Regina Elena class fired a heavier shell. The Regina Margheritas were lost during the war, the Regina Elenas scrapped after the war.
