Report on a captured Japanese Model 97 150-mm mortar, from Intelligence Bulletin, February 1945. [Editor's Note: The following article is wartime information on enemy equipment and tactics published for Allied soldiers. More accurate data on Japanese weapons and equipment is available in postwar publications.]

 

THE 150-MM MORTAR The Japanese Army, which has relied heavily upon the trench mortar for fire support, has developed a 150-mm mortar. Called a "medium" mortar by the Japanese, this Model 97 (1937) 150-mm weapon is a conventional smooth-bore, muzzle-loading, bipod-mounted mortar of sturdy construction. Captured on Peleliu Island, this weapon is the largest Japanese mortar yet found. There it was emplaced in a concrete pit with the muzzle level with the top of the pit. This 150-mm mortar, which resembles in design the standard U.S. 81-mm mortar, weighs 770 pounds complete with sight, and fires a conventional type of high-explosive shell weighing approximately 57 pounds. The weapon is sighted by means of a 3-power panoramic elbow telescope, and the Japanese claim it will throw a projectile a maximum 2,187 yards. Bursting radius of the shell is reported to be 65 feet, with some fragments thrown 100 feet further. For transport, the mortar--including the sight--breaks down into these five component parts: Tube   . . . . .   257 pounds Base Plate   . . . . .   337 pounds Bipod and elevating gear   . . . . .   100 pounds Traversing gear, shock-absorbers, and mortar clamps    . . . . .   74.5 pounds Sight   . . . . .    1.5 pounds The tube is 75.37 inches long and has a reinforcing muzzle band, while the heavy, ribbed-steel base plate measures 47.75 inches by 35.5 inches. The Japanese Model 97 150-mm mortar, largest enemy weapon of this type yet encountered by U.S. troops in the Pacific. The 150-mm mortar shell weighs approximately 57 pounds. The bursting radius is reported to be 65 feet. The weapon is assembled, adjusted for fire, and operated like the U.S. 81-mm mortar. However, the firing mechanism resembles that of the Japanese Model 99 81-mm mortar, using a firing-pin cam shaft built into the base-cap, rather than a fixed firing pin. The Japanese are known to have another Model 97 150-mm mortar, which has not yet been encountered. It is reported to weigh 1,540 pounds and to have a maximum range of 3,828 yards. There is a possibility that this mortar may be installed on a mobile mount.

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