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Type 97 grenade

The Type 97 hand (九七式手榴弾, Kyūnana-shiki Teiryūdan) was a standard-issue fragmentation employed by the and during the Second (1937–1945) and (1939–1945). It consisted of a cylindrical, serrated steel body designed to produce upon detonation, filled with approximately 2 ounces (57 grams) of powdered explosive, and weighed about 19 ounces (532 grams) with dimensions of roughly 4 inches (102 mm) in height and 2 inches (51 mm) in diameter. The 's system featured a 4-5 second delay, activated manually by screwing the into an inertia weight, removing the , and striking the head against a hard surface to ignite a black powder delay train leading to a . Introduced in 1937 as a simplified successor to the earlier , the Type 97 differed primarily in its solid base, which eliminated the rifle-propelled launch capability of its predecessor, restricting it exclusively to hand-thrown use. Manufactured primarily at facilities like the 1st Arsenal during the Showa era (with examples dated to 1941), it bore minimal markings such as ink-stamped production dates on the base and occasional paper labels, often featuring a red-painted top for identification. The design emphasized portability and ease of production amid wartime demands, but its impact-activated proved unreliable, sometimes detonating prematurely and posing risks to the thrower. In combat, the Type 97 saw widespread deployment across Pacific theater battles, including Okinawa, where its fragmentation pattern—producing small, low-velocity shards—resulted in a limited kill radius compared to Allied equivalents like the U.S. . This reduced lethality was evident in accounts of soldiers surviving direct impacts by covering the device, highlighting its weaker explosive power and inconsistent performance. By , began transitioning to the more versatile , though the Type 97 remained in service until Japan's surrender in 1945 due to production constraints and ongoing shortages.

History

Development

The Type 97 hand grenade was designed in 1936 by engineers at the Imperial Japanese Army's technical bureau as an improved fragmentation weapon for infantry use. It entered formal service in 1937, becoming the standard-issue grenade for front-line troops during the Second Sino-Japanese War, where its reliability was prioritized for close-range assaults in urban and trench environments. This design evolved directly from the introduced in 1931, which had been primarily intended for multi-role use as a hand-thrown or / via attached charges. To remedy the Type 91's limitations—such as its longer delay that risked premature explosion in hasty throws and its cumbersome adaptability for launchers—the incorporated a shortened 4-5 second pyrotechnic delay and a solid base plug that eliminated compatibility, dedicating it solely to hand-throwing. These changes enhanced explosive effectiveness through approximately 2 ounces (57 grams) of powdered filling, which produced more consistent fragmentation from the grenade's serrated cast-iron body compared to the Type 91's variable performance in hand use. Initial testing focused on the system's reliability under conditions, leading to the retention and refinement of the percussion striker mechanism inherited from the Type 91. Unlike pin-pull time fuzes common in other armies, which began delay upon pin removal, the Type 97's required arming by threading the , withdrawing a , and then striking the head against a hard surface to ignite the delay element—ensuring the thrower could precisely time initiation for better control in dynamic assaults. This approach addressed reliability issues in the Type 91 by reducing accidental activation risks during carrying.

Production

The Type 97 grenade was primarily manufactured by arsenals, with the 1st Tokyo Arsenal serving as a key producer during its service life. Production commenced following its adoption in and continued through , with large numbers produced to meet demands for frontline use. These facilities employed standardized assembly processes, integrating the cast components, installation, and explosive filling under controlled conditions to ensure reliability. The grenade's body consisted of a cylindrical shell, sourced from domestic foundries to leverage Japan's industrial base for fragmentation effects via external serrations. The explosive filling was approximately 2 ounces (57 grams) of powdered , produced at specialized chemical plants such as those operated by the Army's munitions divisions. This combination of materials allowed for a total weight of about 19 ounces (539 grams), balancing portability with lethality. As wartime resource shortages intensified after 1942, production adapted with simplified assembly lines to conserve materials and labor, resulting in variations such as aluminum-bodied grenades that reduced weight but potentially affected durability. These changes led to inconsistencies in quality, including uneven serrations or fuze tolerances, though core specifications were maintained. Grenades bore markings for quality control and traceability, typically including imperial stamps, arsenal identifiers like those for , and lot numbers inked on paper labels affixed to the base, along with production dates in the Showa era . The body was painted black, with the head in red to denote its high-explosive nature.

Design

Construction

The Type 97 grenade consists of a cylindrical body engineered for fragmentation effects, featuring distinctive serrated "pineapple" grooves along its exterior surface to promote the dispersal of upon . These grooves form approximately 50 segments, creating irregular fragments that enhance the grenade's antipersonnel lethality by increasing the number and coverage of projectiles. The body is constructed from with a carbon content of about 3.7%, providing durability while allowing for controlled breakup during . Overall, the grenade weighs approximately 0.53 kg (19 oz or 532 g) when filled and measures 10.2 (4 inches) in length with a diameter of roughly 5.1 (2 inches), making it compact for hand-throwing. The interior is loaded with 65 g of powdered as the high-explosive filling, inserted through a filling at the upper end before sealing. The exterior is painted black for , with a red-painted top plate or fuze cover to visually indicate the presence of the explosive charge and distinguish it from inert training versions. A key structural difference from the earlier is the solid base design of the , which lacks threading or attachments for propellants or stabilizers, limiting it exclusively to hand-thrown use. The assembly, housed in a or tube screwed into the top, integrates the mechanism, including an inertia-operated lever secured by a double-pronged safety clip (pin) that passes through slots in the striker cover. This lever, along with a creep spring and , is machined as a single unit in later variants for reliability, and the entire assembly is retained by a screw to prevent accidental activation during handling.

Operation

The Type 97 grenade employs a percussion that requires specific preparatory steps for arming. To prepare the grenade for use, the operator screws the steel into the brass weight at the top until it protrudes slightly from the base, ensuring the pin is positioned to strike the primer upon impact. A double brass , which passes through the housing, is then withdrawn to free the . This acts as the primary safeguard against accidental activation during handling or transport. Activation occurs through an impact-based system rather than a traditional pull-pin and release. With the removed, the operator strikes the protruding inertia weight firmly against a hard surface, such as a , stock, or the ground. This overcomes the creep , driving the into the primer cap and igniting a pyrotechnic delay train composed of black powder rolled in paper tubing. The delay lasts 4 to 5 seconds, during which the must be thrown to avoid endangering the user. Following the delay, the train reaches a booster pellet, which detonates the main charge of approximately 65 grams, fragmenting the serrated cast-iron body. Trained soldiers could typically achieve a throwing range of 30 to 40 meters with the 530-gram , depending on and conditions, though the demanded precise timing to prevent self-injury. The design's reliance on manual striking introduced notable risks, including premature from excessive force or rough handling, as the lacked a secondary interlock. Field reports highlighted the 's unreliability, with frequent failures in primer ignition leading to duds if the strike was insufficient, contributing to its reputation as hazardous for operators. No separate is used in the firing train, simplifying construction but potentially exacerbating inconsistency in performance.

Operational Use

World War II

The Type 97 grenade served as the primary fragmentation hand grenade for the (IJA) and Navy (SNLF) throughout , particularly in during the and the Pacific Theater. Introduced as standard issue in , it was widely deployed in urban and jungle environments where its compact design allowed for rapid throws in confined spaces. In island-hopping campaigns such as and , Japanese troops relied on it for suppressing Allied advances in dense terrain, often lobbing volleys from concealed positions to disrupt enemy patrols. It also saw use in battles like and , where intense amplified its role in engagements. During banzai charges and defensive stands, the Type 97 proved instrumental in desperate assaults, with its fragmentation radius of about 5 meters inflicting casualties in tight jungle fighting. For instance, at the River on in August 1942, Japanese soldiers incorporated grenades into their nighttime banzai attacks, though such tactics resulted in heavy Japanese losses. The grenade's small, low-velocity fragments were less lethal over distance compared to Allied designs but caused high-impact wounds in close proximity, contributing to the brutal attrition of Pacific engagements. In reliability, the Type 97 lagged behind the U.S. due to its impact-activated , which was prone to duds if not struck firmly enough on a hard surface, exacerbated by deterioration in humid conditions. soldiers received training to mitigate this by slamming the grenade against their helmets or before throwing, ensuring activation in high-stakes scenarios. Similarly, in the 1944 Philippines campaign, IJA units employed the in defensive pockets around and , hurling them during close assaults amid the campaign's fierce house-to-house battles.

Post-War Conflicts

Following the in 1945, stockpiles of Type 97 grenades were captured and repurposed by Chinese communist forces during the (1945–1949), where they were employed against Nationalist troops as part of broader reuse of military equipment seized from abandoned arsenals in and other regions. In the (1945–1949), independence fighters extensively used leftover Type 97 grenades from WWII stockpiles to arm guerrilla operations against colonial forces, leveraging the weapon's availability in former occupation zones for ambushes and defensive actions. These grenades proved effective in , with remnants discovered and disposed of by the as late as 2022, highlighting their prolonged circulation in the region. The appeared in limited capacities during the (1950–1953), where smuggled stocks were utilized by North Korean and Chinese forces in skirmishes, as noted in contemporary U.S. Army identification handbooks that described its activation method and explosive yield for frontline recognition. Rare modern discoveries of WWII-era grenades continue through clearance, underscoring the grenade's extended logistical footprint. The legacy of the persists as an ongoing hazard from buried WWII caches across Pacific islands, where corrosion and concealment pose risks to civilians and construction workers decades later. efforts, initiated post-1950 and intensified by organizations like the since the 1990s, have targeted such ordnance in areas like the and ; for instance, in September 2024, U.S. explosive ordnance disposal technicians safely removed a live from a construction site at on , preventing potential detonation during development activities. These operations address an estimated thousands of unexploded items, reducing annual incidents that have claimed lives in remote communities since the war's end.

References

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