As the Type 41 12-inch (305 mm) 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.

Japan purchased a total of 44 of these weapons for use on the four ships of the Fuji and Shikishima class, and the battleships Asahi and Mikasa.

In combat at the Battle of the Yellow Sea in the Russo-Japanese War, the Japanese battleships Asahi, Shikishima and Mikasa all had one of their main guns taken out of action due to premature bore detonations.

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.