Type 98 320mm Mortar

During the Second World War the Japanese made some use of large spigot mortars. These large, improbable and impractical looking weapons could launch a massive bomb up to a kilometre. 

In the late 1930s Japan developed a large 320mm spigot mortar, the 九八式臼砲 or Type 98 mortar, which fired a huge 300kg or 660lb high explosive finned bomb. Characterised by a large wooden base, seemingly made up of a series of planks, with a 225lb metal spigot at its centre. The Type 98′s projectile was nearly 5 feet tall and had 4 fins to stabilise it in flight. The bomb   itself weighed 225lbs, and could launch its massive bomb up to 1,000 yards, with the range varied by the size of powder charge used. The life-span of the spigots was believed to be fewer than 10 rounds.

Photos from a US Army briefing note appearing in ‘Weekly Intelligence’ (source)

The bomb itself split into three parts with the nose packed with a fuse and explosives, a body casing and a propellant charge. 

Very few photographs of the Type 98 mortars survive but the large wooden bases appear to have been frequently placed on earth mounds to brace against the recoil forces and also provide some rudimentary, gross aiming. The Type 98 saw action during the Battle of Bataan and the battles for Iwo Jima and Okinawa.

Sources:

Weekly Intelligence Review Vol.1, No.70, 17 & 35
Closing In: Marines in the Seizure of Iwo Jima, Col. J.H. Alexander (source)

If you enjoy the content please consider supporting Historical Firearms through Patreon!