The was a "last-ditch" hand grenade developed by the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender ...

in the closing stages of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

History and development

By late 1944 and early 1945, much of the industrial infrastructure of Japan had been destroyed by Allied strategic bombing, and there was a growing shortage of raw materials due to Allied

naval blockade A navy, naval force, or maritime force is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake-borne, riverine, littoral, or ocean-borne combat operations and related functions. It includ ...

s and submarine warfare. Lacking in metals to mass-produce hand grenades in the vast quantities that would be needed against the projected Allied invasion of Japan, the Imperial Japanese Navy Technical Bureau developed a design for a cheap, easy-to-make grenade made of

ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...

porcelain Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises mainl ...

materials.

Kiln A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been used for millennia to turn objects made from clay int ...

s famous for the production of traditional

Japanese pottery , is one of the oldest Japanese crafts and art forms, dating back to the Neolithic period. Kilns have produced earthenware, pottery, stoneware, glazed pottery, glazed stoneware, porcelain, and blue-and-white ware. Japan has an exceptional ...

, such as

Arita Arita may refer to: *Arita (surname) *Arita, Saga, a town in Saga Prefecture, Japan :* Arita ware, a kind of Japanese porcelain made in the area around the town * ''Arita'' (skipper), a genus of butterflies in the grass skipper family *Arita, a br ...

, Bizen and

Seto Seto may refer to: Places * Seto, Aichi, production place of Japanese pottery and venue of Expo 2005 * Seto, Ehime, facing the Seto Inland Sea *Seto, Okayama, adjacent to Okayama, in Okayama Prefecture *Seto Inland Sea of Japan * Setomaa (''Seto ...

were pressed into service to manufacture these relatively crude weapons. There were a tremendous number of variants on shape, size and color, because the design depended on each kiln.

Design

The Type 4 grenade had a fragmentation body made of

terra cotta Terracotta, terra cotta, or terra-cotta (; ; ), in its material sense as an earthenware substrate, is a clay-based unglazed or glazed ceramic where the fired body is porous. In applied art, craft, construction, and architecture, terracotta ...

or porcelain materials. The grenade was round-shaped with a bottle neck with a rubber cover and a simple

fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...

. This detonator was no more than a

blasting cap A detonator, frequently a blasting cap, is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the last two being the most common. The commercial use of explosives uses electri ...

crimped on to a five-second length of fuse. The other end of the fuse, which was outside the rubber plug, was covered with a

match A match is a tool for starting a fire. Typically, matches are made of small wooden sticks or stiff paper. One end is coated with a material that can be ignited by friction generated by striking the match against a suitable surface. Wooden matc ...

-head composition. A slip-on rubber cap covered the whole neck, and fuse. A small, loose wooden block with an abrasive composition on one side was contained in the rubber fuse cover.

Combat record

Type 4 grenades were passed out in large quantities to

civil defense Civil defense ( en, region=gb, civil defence) or civil protection is an effort to protect the citizens of a state (generally non-combatants) from man-made and natural disasters. It uses the principles of emergency operations: prevention, miti ...

organizations, such as the

Volunteer Fighting Corps were armed civil defense units planned in 1945 in the Empire of Japan as a last desperate measure to defend the Japanese home islands against the projected Allied invasion during Operation Downfall (''Ketsugo Sakusen'') in the final stages of ...

, ''

Yokusan Sonendan The was an elite paramilitary youth branch of the ''Imperial Rule Assistance Association'' political party of wartime Empire of Japan established in January 1942, and based on the model of the German Sturmabteilung (stormtroopers). Members rec ...

'', and to reservist organizations involved in preparations against the possible invasion of the

Japanese home islands The Japanese archipelago (Japanese: 日本列島, ''Nihon rettō'') is a group of 6,852 islands that form the country of Japan, as well as the Russian island of Sakhalin. It extends over from the Sea of Okhotsk in the northeast to the East Chi ...

by Allied forces. They were also supplied to front line combat troops in large quantities, and are known to have been employed at the Battle of Iwo Jima and

Battle of Okinawa The , codenamed Operation Iceberg, was a major battle of the Pacific War fought on the island of Okinawa by United States Army (USA) and United States Marine Corps (USMC) forces against the Imperial Japanese Army (IJA). The initial invasion of ...

.Lone Sentry: New Weapons Captured at Ormoc, Japanese (U.S. WWII Intelligence Bulletin, March 1945)
/ref>

Photo gallery

File:Type4Grenade.jpg, Schematic of components File:97-1-B_Japanese,_Grenade,_Type_4,_Ceramic.jpg File:Japanese porcelain grenade.jpg

Notes

References

* *

External links

{{Japanese WWII infantry weapons World War II infantry weapons of Japan 44 Fragmentation grenades Hand grenades of Japan Weapons and ammunition introduced in 1944