WW2 Legacy UXO -- Pacific Theater

Scope: Japanese and US ordnance from 1937-1945 still encountered as unexploded ordnance (UXO) across the Pacific islands, Japan, Philippines, China, and Southeast Asia. This remains a daily EOD problem 80+ years after the end of hostilities.

WARNING -- AGED ORDNANCE HAZARDS: All items in this file are 80+ years old. Explosive fills have degraded, fuzes have corroded, and chemical compositions have changed unpredictably. Every item should be treated as maximum sensitivity until proven otherwise. Picric acid forms shock-sensitive metal picrates with iron/copper casings. Mercury fulminate detonators become MORE sensitive with age. TNT can exude nitroglycerin-like compounds. Chemical fills may have leaked or polymerized. Do NOT assume any standard RSP applies without current condition assessment.

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TABLE OF CONTENTS

1. Japanese Explosive Compounds
2. Japanese Aerial Bombs
3. Japanese Mortar Rounds
4. Japanese Artillery -- Type 92 Battalion Gun
5. Japanese Naval Mines
6. Japanese Torpedoes
7. Japanese Hand Grenades
8. Japanese Incendiary / Cluster Munitions
9. Japanese Chemical Munitions
10. Japanese Suicide Weapons
11. US General Purpose Bombs
12. US Incendiary Munitions
13. US Naval Gunfire Rounds
14. US Torpedoes
15. US Mines
16. US Underwater Demolition Charges
17. Locations Where WW2 UXO Is Still Found
18. Aged Ordnance Hazards -- General Guidance
19. Sources

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Japanese Explosive Compounds

Understanding Japanese explosive fills is critical because aging characteristics differ dramatically from US/Allied fills.

Shimose (Picric Acid / Trinitrophenol)

• Designation: Shimose bakuyaku
• Composition: Pure picric acid (2,4,6-trinitrophenol)
• Used in: Hand grenades (Type 91, 97, 99), sea mines, early aerial bombs, artillery shells
• CRITICAL AGING HAZARD: Picric acid reacts with metal casings (iron, copper, lead, zinc) to form metal picrates over decades. Anhydrous metal picrates are EXTREMELY shock-sensitive -- some approach mercury fulminate sensitivity. Iron picrate formation is the most common in steel-cased ordnance. Dry picric acid (below 10% water content) is itself highly sensitive to heat, shock, and friction.
• EOD Significance: Japanese grenades were internally coated with protective varnish to slow picrate formation, but after 80+ years this varnish has failed in most specimens. Assume ALL picric-acid-filled Japanese ordnance has formed metal picrates.

Type 88 Explosive

• Designation: Type 88 bakuyaku (Model 1928)
• Composition: Improved picric acid formulation with stabilizers
• Used in: Naval mine charges (Type 93 mine contained 220 lbs Type 88), artillery fuzes
• Aging: Similar picrate formation risks as Shimose but somewhat more stable

Type 91 Explosive (TNA)

• Designation: Type 91 bakuyaku (Model 1931)
• Composition: Trinitroanisole (TNA)
• Used in: Armor-piercing bombs (Type 99 No. 80), APC naval shells, torpedo warheads
• Properties: Considered particularly insensitive compared to picric acid. More stable aging profile.
• Aging: Less prone to metal salt formation than picric acid but can still degrade over 80+ years

Type 98 Explosive

• Designation: Type 98 bakuyaku
• Composition: 70% trinitroanisole / 30% hexanitrodiphenylamine (hexyl)
• Used in: Aerial bombs (Type 97 series and others)
• Aging: More stable than Shimose but hexyl component can crystallize under certain conditions

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Japanese Aerial Bombs

Type 97 Aerial Bombs (50 kg class)

Identification

• Designation: Type 97 No. 6 (Navy designation system)
• Type: Aerial bomb, general purpose / incendiary variants
• Category: Air-to-ground
• Country of Origin: Japan
• Era: 1937 onward (Imperial Year 2597)

Physical Characteristics

• Weight: ~60 kg (132 lbs) total
• Explosive Fill: ~23 kg (51 lbs) Type 98 explosive
• Fuzing: Type 16 A-4 nose fuze (fan-initiated / vane-armed)
• Variants: HE, incendiary (Type 97 50 kg incendiary)

Current Condition (80+ years)

• Thin-walled casings heavily corroded
• Fuze vane mechanisms may be jammed or free-spinning
• Explosive fill may have shifted or exuded through casing cracks
• Incendiary variants: thermite/magnesium fill may still be reactive

EOD Hazards

• Fan-initiated fuzes can be armed by minimal disturbance if vane mechanism is corroded in partial-arm position
• Type 98 explosive fill crystallization possible
• Booster charges may have separated from main fill

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Type 99 Aerial Bombs (30 kg through 800 kg)

Type 99 No. 25 Model 1 Ordinary (250 kg / 551 lbs)

Identification

• Designation: Type 99 Number 25 Model 1 Ordinary
• Type: Aerial bomb, anti-shipping / general purpose
• Era: 1939 (Imperial Year 2599)

Physical Characteristics

• Total Weight: 250 kg (551 lbs)
• Explosive Fill: ~62 kg (136 lbs) high explosive
• Fuzing: Impact-initiated with 0.2 second delay
• Design: Semi-armor-piercing; intended to penetrate ordinary steel plating then detonate 20-40 feet (6-12 m) inside target

EOD Hazards

• Delay fuze mechanism contains chemical or mechanical delay elements that may have degraded
• Semi-AP construction means thicker casing, slower corrosion, but explosive may be more confined
• 0.2 second delay fuze: if armed but unfired, internal delay mechanism in unknown state

Type 99 No. 80 Mark 5 (800 kg / 1,760 lbs -- Pearl Harbor bomb)

Identification

• Designation: Type 99 Number 80 Mark 5
• Type: Armor-piercing aerial bomb (converted from 16" battleship shells)
• Historical Context: Used at Pearl Harbor, December 7, 1941

Physical Characteristics

• Total Weight: 800 kg (1,760 lbs)
• Explosive Fill: 23 kg (50 lbs) Type 91 explosive (TNA)
• Fuzing: Two base fuzes with 0.2 second delay
• Construction: Remanufactured from obsolete 41 cm (16") battleship armor-piercing shells
• Casing: Extremely thick forged steel (original AP shell body)

EOD Hazards

• Heavy forged steel casing resists corrosion better than thin-walled bombs
• Small explosive charge relative to total weight but Type 91 fill is relatively stable
• Base fuze configuration: fuzes insensitive enough to require impact on armor plate to initiate
• Dual fuze system increases complexity of any RSP
• If found underwater: thick casing may appear intact but internal corrosion may have compromised fuze train

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Japanese Bomb Fuze Classification (Allied System)

Japanese bomb fuzes were classified by the Allies using a letter-number system:

• A -- Nose impact fuze
• B -- Tail (base) impact fuze
• C -- Long delay fuze (nose or tail)
• D -- Aerial burst fuze (nose or tail)
• E -- Protective fuze (nose or tail)

Suffixed numeral indicates order of recovery by Allied forces. Small letter in parentheses (a, b, c) indicates sub-variants.

NOTE: The actual Japanese Navy fuze designation system was unknown to the Allies until after the war. Field-recovered items may bear Japanese markings that do not correspond to Allied classification.

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Japanese Mortar Rounds

Type 89 50mm Grenade Discharger Round ("Knee Mortar")

Identification

• Designation: Type 89 (for the launcher; rounds designated by fill type)
• Type: Mortar / grenade launcher round
• Caliber: 50mm
• Country of Origin: Japan
• Era: 1929 (Imperial Year 2589)

Physical Characteristics

• Diameter: 50mm (2 inches)
• Overall Height: 5.75 inches (146 mm)
• Weight: ~910 g (2 lbs)
• Variants: HE, incendiary, smoke
• Fuzing: Type 88 instantaneous impact fuze

EOD Hazards -- Aged Condition

• Small size means often overlooked or mistaken for debris
• Type 88 impact fuze: after 80+ years of corrosion, firing pin may be corroded in near-strike position
• HE fill (picric acid in early rounds, TNT in later) may have exuded
• Extremely common find across all Pacific island battlefields
• Often found in clusters near former Japanese defensive positions

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Type 97 81mm Mortar Round

Identification

• Designation: Type 97 81mm Infantry Mortar system; fires Type 100 (Type 00) HE round
• Type: Mortar projectile
• Caliber: 81mm
• Country of Origin: Japan
• Era: 1937 (Imperial Year 2597)

Physical Characteristics

• Light HE Round (Type 97/100):
  • Weight: ~3.3 kg (7.3 lbs)
  • Explosive fill: ~0.54 kg TNT main charge with picric acid booster
• Heavy HE Round (Type 00):
  • Length: 12.87 inches (327 mm)
  • Weight: 6.93 lbs (3.14 kg) [some sources: up to 6.5 kg]
  • Explosive fill: ~1 lb (0.45 kg) TNT
• Muzzle Velocity: 196 m/s
• Maximum Range: 2,800-3,000 m

EOD Hazards -- Aged Condition

• Picric acid booster is the primary concern -- will have formed iron picrate with steel body
• Tail fin assembly may have separated, making rounds harder to identify
• Propellant increments may have degraded but can still be energetic
• Very common UXO find across Pacific; thousands fired per engagement
• Often found partially buried with only nose or tail fin visible

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Japanese Artillery -- Type 92 Battalion Gun

Type 92 70mm Battalion Gun Shells

Identification

• Designation: Type 92 70mm Battalion Gun
• Type: Light howitzer projectile
• Caliber: 70mm (2.75 inches)
• Country of Origin: Japan
• Era: 1932 (Imperial Year 2592)

Physical Characteristics

• Shell Types: HE, Smoke, HEAT (hollow charge, introduced 1943)
• Muzzle Velocity: 198 m/s (650 ft/sec)
• Maximum Range: 2,785 m
• HEAT Round: Could penetrate up to 90mm of armor (confirmed by US tests with captured rounds in Philippines)

EOD Hazards -- Aged Condition

• HEAT rounds contain shaped charge copper liner -- if corroded, copper fragments may be displaced
• HE rounds: standard Japanese explosive fills (Shimose or TNT variants)
• Very widely deployed weapon -- found across all Pacific battlefields
• Short range meant these were used in close defensive positions; UXO often found in and around former bunker complexes
• Fuzing: standard Japanese artillery fuzes, impact-detonated

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Japanese Naval Mines

Type 93 Naval Mine (Model 1)

Identification

• Designation: Type 93 Model 1
• Type: Moored contact mine (Hertz horn type)
• Category: Naval mine, intended for aerial delivery
• Country of Origin: Japan
• Era: 1933 (Imperial Year 2593)

Physical Characteristics

• Total Weight: 700 kg (1,543 lbs)
• Explosive Fill: 100 kg (220 lbs) Type 88 high explosive
• Depth Range: Minimum 25 feet, maximum 3,527 feet
• Detonation Mechanism: Hertz horn -- each horn contains sulphuric acid. Contact with horn breaks acid container, energizing a lead-acid battery that fires the detonator

Current Condition (80+ years)

• Mooring cables have corroded and broken; mines may have drifted or settled on seafloor
• Hertz horns: sulphuric acid containers may have leaked or crystallized
• External casing heavily corroded in saltwater; barnacle and coral encrustation common
• Internal battery electrolyte may have leaked, creating secondary chemical hazard
• Type 88 explosive fill: picric acid derivative, prone to metal picrate formation with corroded steel casing

EOD Hazards

• CRITICAL: Hertz horn mechanism can still function if acid containers are intact -- ANY contact with horns can detonate
• Corroded horns may be structurally weakened; minimal force could break them
• Mines found on beaches or in shallows may have been wave-tumbled, making orientation unpredictable
• Internal explosive has had 80+ years of contact with corroding steel casing
• Type 88 fill sensitivity changes are unpredictable

Historical Context

• Almost ALL Japanese mines were Hertz horn construction
• Japan did NOT develop magnetic (influence) mines
• Some captured British mines (A Mark I-IV) were laid by Japan off Balikpapan in 1945

Underwater/Marine Degradation

• Saltwater accelerates corrosion of steel casings
• Biofouling can mask mine shape and horn positions
• Mines in tropical waters corrode faster due to higher temperatures, salinity, and dissolved oxygen
• Some mines have been incorporated into coral reef structures

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Type 5 Moored Contact Mine (earlier design)

Physical Characteristics

• Design: 1916 vintage
• Explosive Fill: 80 kg (176 lbs) picric acid (Shimose)
• Type: Hertz horn moored contact

EOD Hazards

• Oldest Japanese mine type still potentially encountered
• Pure picric acid fill in steel casing: MAXIMUM metal picrate formation risk after 100+ years
• Treat as extremely shock-sensitive

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Japanese Torpedoes

Type 93 "Long Lance" Torpedo

Identification

• Designation: Type 93 Torpedo
• Allied Name: "Long Lance" (postwar designation by Samuel Eliot Morison)
• Type: Ship-launched oxygen-fueled torpedo
• Country of Origin: Japan
• Era: 1933 (Imperial Year 2593)

Physical Characteristics

• Length: 9.0 m (29.5 ft)
• Diameter: 610 mm (24 in)
• Total Weight: 2,700 kg (5,952 lbs)
• Warhead: 490 kg (1,080 lbs) Type 97 explosive
• Propulsion: Oxygen-enriched air (kerosene fuel + compressed oxygen)
• Speed: 36-50 knots (depending on range setting)
• Range: Up to 40 km at 36 knots; 20 km at 50 knots

Where Still Found

• Wrecks in Chuuk (Truk) Lagoon: found in holds of sunken ships (San Francisco Maru, Seiko Maru)
• Harbor floors across former Japanese naval bases
• Partially embedded in reef structures

EOD Hazards -- Aged Condition

• Oxygen flask may still hold residual pressure after 80+ years
• Warhead explosive (Type 97): relatively stable but 80+ years of saltwater exposure unknown
• Propulsion section: kerosene residue + oxygen system creates fire/explosion risk if disturbed
• Large size makes in-situ disposal challenging
• Contact pistol mechanism: unknown armed/safe state in corroded specimens

Underwater/Marine Degradation

• Steel torpedo body heavily corroded but recognizable shape often preserved
• Warhead section may be breached, leaching explosive compounds into water
• Propeller and tail section often intact (bronze/brass components resist saltwater corrosion)

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Type 91 Aerial Torpedo

Identification

• Designation: Type 91 Torpedo (aerial variant)
• Type: Air-launched torpedo
• Historical Context: Modified for shallow-water attack at Pearl Harbor (wooden stabilizer fins added)
• Diameter: 450mm (17.7 in)

EOD Hazards

• Similar to Type 93 but smaller
• Pearl Harbor specimens may still exist on harbor floor
• Wooden anti-roll stabilizers long since deteriorated

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Kaiten Human Torpedo

Identification

• Designation: Kaiten (meaning "Return to Heaven")
• Type: Manned suicide torpedo
• Country of Origin: Japan
• Era: 1944-1945

Physical Characteristics -- Type 1 (primary operational model)

• Warhead: 1,550 kg (3,420 lbs) explosive
• Construction: Modified Type 93 torpedo with enlarged warhead and pilot compartment
• Speed: 12 knots cruising / 30 knots maximum
• Range: 42 nautical miles maximum
• Operating Depth: Up to 250 feet (76 m)
• Detonation: Inertial pistol AND electrical pistol controlled by pilot

EOD Hazards -- Aged Condition

• MASSIVE warhead (3x the standard Type 93) -- 1,550 kg of explosive
• Dual detonation system (inertial + electrical) doubles initiation risk
• Found on seafloor near former Japanese submarine bases and at attack sites
• Pilot compartment creates additional void space where gases/water can accumulate
• Electrical detonation circuit: corroded wiring creates unpredictable short-circuit risk

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Japanese Hand Grenades

Type 97 Fragmentation Hand Grenade

Identification

• Designation: Type 97
• Type: Fragmentation hand grenade
• Country of Origin: Japan
• Era: 1937 (Imperial Year 2597) -- standard IJA/IJN SNLF grenade

Physical Characteristics

• Length: 3.5 inches (89 mm)
• Diameter: 1.625 inches (41 mm)
• Weight: 0.8 lbs (363 g)
• Body: Segmented cast steel (for fragmentation)
• Explosive Fill: Cast picric acid (Shimose)
• Fuze Delay: 4-5 seconds
• Arming: Strike igniter -- tap base against hard surface to initiate delay train

Current Condition (80+ years)

• Segmented body often intact but heavily corroded
• Picric acid has reacted with steel body to form iron picrate
• Protective interior varnish has failed
• Fuze delay train: creep igniter mechanism may have degraded
• External markings largely obliterated by corrosion

EOD Hazards

• EXTREME SENSITIVITY: Picric acid + 80 years of metal contact = shock-sensitive metal picrates throughout
• Strike igniter mechanism may fire from minimal impact
• Fragmentation body means even partial detonation is lethal at close range
• Very commonly found across ALL Pacific battlefields
• Often found in bunkers, caves, and fighting positions
• Small size means easily disturbed by construction equipment or foot traffic

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Type 99 Hand Grenade ("Kiska Grenade")

Identification

• Designation: Type 99
• Allied Name: "Kiska grenade" (US Army designation after Kiska recovery)
• Type: Fragmentation hand grenade (improved Type 97)
• Era: 1939 (Imperial Year 2599)

Physical Characteristics

• Length: 3.5 inches (89 mm)
• Diameter: 1.625 inches (41 mm)
• Weight: ~0.8 lbs (363 g)
• Body: Smooth cylindrical cast steel, flanged on both ends (NOT segmented like Type 97)
• Explosive Fill: 58 g (2.0 oz) cast picric acid
• Interior: Coated with protective varnish (to slow picric acid reaction with steel)

Key Differences from Type 97

• Smooth body (not segmented) -- different visual profile
• Flanged ends for easier gripping
• Interior varnish coating (design acknowledgment of picrate problem)
• Same strike-igniter arming mechanism

EOD Hazards

• Same picric acid / metal picrate hazards as Type 97
• Smooth body may make field identification more difficult (can be mistaken for pipe fragments)
• Protective varnish has certainly failed after 80+ years -- assume full picrate contamination

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Japanese Incendiary / Cluster Munitions

Type 3 Cluster Bomb / Submunitions

Identification

• Designation: Type 3 (various sub-designations)
• Type: Cluster bomb with HE and incendiary submunitions
• Variants: Type 3 1/2 kg HE cluster bomb submunition; Type 2 1/3 kg HEAT cluster bomb submunition
• Country of Origin: Japan

Physical Characteristics

• Submunition Weight: 0.5 kg to 1.3 kg individual bomblets
• Parent Container: Carried in dispensers dropped from aircraft
• HEAT Variant: Small shaped-charge anti-vehicle submunition (late war)

EOD Hazards -- Aged Condition

• Small submunitions scatter widely -- difficult to locate all in a given area
• Impact fuzes may or may not have functioned; high dud rate with cluster munitions
• Incendiary variants: thermite/magnesium components may still be reactive
• Found buried in soil across former airfield targets
• Small size makes accidental disturbance by civilians likely

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Japanese Chemical Munitions

Mustard Gas (Yperite) and Lewisite Munitions

Identification

• Designation: Various -- artillery shells, mortar rounds, aerial bombs, drums, pots
• Type: Chemical warfare munitions
• Country of Origin: Japan (produced at Okunoshima island facility)
• Agents: Mustard gas (sulfur mustard), lewisite, diphenylcyanoarsine, hydrogen cyanide, chloroacetophenone, phosgene
• Era: 1937-1945

Production Scale

Okunoshima facility peak monthly production:

• Mustard gas: ~200 tons
• Lewisite: ~50 tons
• Diphenylcyanoarsine: ~80 tons
• Hydrogen cyanide: ~50 tons
• Chloroacetophenone: ~2.5 tons

Scale of Use

• Used against Chinese troops/guerrillas an estimated 2,000 times between 1937-1945
• Estimated 80,000 maimed, 10,000 killed by chemical attacks in China

Where Still Found

• China: 50,000+ projectiles, mortars, aerial bombs, liquid-filled drums and gas-filled pots found scattered over 90+ sites. Japan-China joint destruction operations ongoing since 2010 (Nanjing mobile destruction facility).
• Japan (Offshore): Sea-dumped munitions off Okunoshima and other coastal sites pursuant to postwar "Operation Lewisite"
• Pacific Islands: Sea-dumped stocks at various former Japanese-occupied island locations
• Seafloor legacy: Corroding munitions leaching chemical agents into marine environment

EOD Hazards

• DUAL HAZARD: Chemical agent exposure AND explosive hazard from burster charges
• Mustard gas remains potent for decades -- liquid mustard found in WWI shells 100+ years later
• Lewisite: arsenic-based vesicant, remains hazardous indefinitely
• Corroded casings may be leaking agent -- approach with full MOPP/CBRN protection
• "Yellow shells" designation used for mustard/lewisite-filled Japanese munitions
• Agent may have polymerized into solid mass (still hazardous on disturbance)
• Burster charges (often picric acid) retain all standard aged explosive hazards
• Sea-dumped munitions: saltwater corrosion has breached many casings

Historical Context

• Chemical weapons were deployed extensively in China but NOT used against Western Allies (policy decision by Japanese high command)
• Abandoned in place at war's end across China and Pacific territories
• OPCW-supervised destruction program ongoing

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Japanese Suicide Weapons

Shinyo Explosive Motor Boats

Identification

• Designation: Shinyo (Navy) / Maru-ni (Army)
• Type: Suicide explosive motor boat
• Country of Origin: Japan
• Era: 1944-1945
• Production: 6,197 Shinyo (Navy) + 3,000 Maru-ni (Army) = ~9,200 total

Physical Characteristics

• Length: 19.7 feet (6 meters)
• Displacement: 1.35 tons
• Speed: Design 30 knots; actual 18-23 knots laden
• Warhead: Up to 300 kg (660 lbs) bow-mounted explosive charge
• Detonation: Impact-initiated (crushing of bow completes electrical circuit) OR manual cockpit switch (later models)
• Additional Armament: Two anti-ship rockets on side launchers
• Engine: Reconditioned automobile engines (67 bhp)

Where Still Found

• Sunken/abandoned in harbors and coastal caves across Philippines, Okinawa, and various Pacific islands
• Japanese forces pre-positioned boats in concealed coastal caves
• Hulls in various states of deterioration in shallow water

EOD Hazards -- Aged Condition

• Bow explosive charge: 300 kg is a massive amount of explosive in a corroded, unstable mounting
• Impact detonation circuit: corroded wiring creates unpredictable electrical state
• Some boats had BOTH impact and manual detonation systems
• Rocket munitions on side launchers: may still be armed
• Engine fuel residue: fire hazard
• Found in caves and confined spaces -- limited approach angles

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US General Purpose Bombs

AN-M30 / AN-M30A1 (100 lb GP Bomb)

Identification

• Designation: AN-M30, AN-M30A1
• Type: General purpose aerial bomb
• Weight Class: 100 lbs (nominal)
• Country of Origin: United States

Physical Characteristics

• Total Weight: 49.9 - 52.16 kg (110 - 115 lbs)
• Length: 91.44 cm (36 in)
• Diameter: 20.83 cm (8.2 in)
• Explosive Fill: 24.49 kg Amatol (50/50) or 25.85 kg TNT
• Fuzing: AN-M103 nose fuze (impact) and/or AN-M101 tail fuze; various combinations
• Casing Thickness: Relatively thin-walled

EOD Hazards -- Aged Condition

• Thin casing corrodes rapidly in tropical soil and saltwater
• Amatol fill (pre-1943): ammonium nitrate component hygroscopic, may have absorbed water and swelled
• TNT fill (1943+): can exude dinitrotoluene and form crystals on casing exterior
• Smallest GP bomb -- easily overlooked, often found in quantity
• Nose and tail fuze wells may be corroded open, exposing booster/detonator

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AN-M57 (250 lb GP Bomb)

Identification

• Designation: AN-M57
• Type: General purpose aerial bomb
• Weight Class: 250 lbs (nominal)

Physical Characteristics

• Total Weight: 113.4 - 117.93 kg (250 - 260 lbs)
• Length: 115.32 cm (45.4 in)
• Diameter: 27.68 cm (10.9 in)
• Casing Thickness: 0.69 cm (0.27 in)
• Explosive Fill: 56.11 kg Amatol or 58.51 kg TNT

EOD Hazards -- Aged Condition

• Same fill-related hazards as AN-M30 but with double the explosive weight
• Casing corrosion exposes fill to moisture and oxygen
• Commonly found across Pacific island targets
• Fuze wells: corrosion may have created pathways for water intrusion to booster

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AN-M64 (500 lb GP Bomb)

Identification

• Designation: AN-M64
• Type: General purpose aerial bomb
• Weight Class: 500 lbs (nominal)

Physical Characteristics

• Total Weight: 226.8 - 242.67 kg (500 - 535 lbs)
• Length: 182.37 - 229.61 cm (71.8 - 90.4 in)
• Diameter: 59.18 cm (23.3 in)
• Explosive Fill: 118.9 - 124.28 kg TNT or Amatol

EOD Hazards -- Aged Condition

• Significant explosive weight -- 120+ kg of fill
• Commonly dropped on Pacific island targets; high-frequency UXO find
• Casing corrosion in tropical soils can be severe
• Often found during construction excavation at depth

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AN-M65 (1,000 lb GP Bomb)

Identification

• Designation: AN-M65
• Type: General purpose aerial bomb
• Weight Class: 1,000 lbs (nominal)

Physical Characteristics

• Total Weight: 437.72 - 449.05 kg (965 - 990 lbs)
• Length: 170.43 cm (67.1 in)
• Diameter: 47.75 cm (18.8 in)
• Casing Thickness: 1.27 cm (0.50 in)
• Explosive Fill: 240.4 kg Amatol or 253.10 kg TNT

EOD Hazards -- Aged Condition

• Quarter-ton of explosive: requires evacuation radius planning for disposal
• Thicker casing (1.27 cm) provides some corrosion resistance but tropical conditions accelerate degradation
• Fuze pockets may have corroded creating water intrusion paths
• Found at major bombardment targets: airfields, port facilities, defensive positions

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AN-M66 (2,000 lb GP Bomb)

Identification

• Designation: AN-M66
• Type: General purpose aerial bomb
• Weight Class: 2,000 lbs (nominal)

Physical Characteristics

• Total Weight: 907.18 - 951.86 kg (2,000 - 2,098 lbs)
• Explosive Fill: 482.17 kg Amatol or 506.66 kg TNT

EOD Hazards -- Aged Condition

• Half-ton of explosive fill: MAJOR disposal operation required
• Largest standard US GP bomb in Pacific service
• Deep penetration on impact means these are found at significant depth in soil
• May require specialized heavy equipment for excavation
• Okinawa discovery in 2024: 2,000 lb bomb found near airport required major evacuation operation
• Fuze condition completely unpredictable after 80+ years underground

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General Notes on US GP Bomb Explosive Fills

• Pre-1943: Standard fill was 50/50 Amatol (ammonium nitrate / TNT mixture)
• 1943 onward: TNT became standard filler as supply increased
• Amatol aging: Ammonium nitrate component is hygroscopic; absorbs moisture, can swell and crack casings, creating exudation pathways
• TNT aging: Can form dinitrotoluene and other degradation products; crystals may form on exterior surfaces; TNT exudation creates shock-sensitive surface deposits
• Booster charges: Tetryl boosters used in most US bombs; tetryl is more sensitive than TNT and degrades to form picric acid over time

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US Incendiary Munitions

AN-M47 Incendiary Bomb (100 lb class)

Identification

• Designation: AN-M47 (series)
• Type: Thin-walled incendiary aerial bomb
• Weight Class: 100 lbs (nominal)
• Country of Origin: United States

Physical Characteristics

• Actual Weight: ~85 lbs (39 kg) with incendiary fill
• Construction: Thin-walled steel body
• Fill: Rubber/gasoline-based incendiary mixture (napalm precursor)
• Central Burster: Explosive charge to disperse incendiary fill
• Fuzing: M108 or M126 series nose impact fuze

EOD Hazards -- Aged Condition

• Thin-walled construction: casings almost certainly breached after 80+ years
• Incendiary fill: rubber/gasoline mixture may have polymerized into solid mass OR may have leaked
• Central burster charge retains explosive potential
• Fuze (M108/M126): impact type, condition unknown after decades
• If fill has leaked, soil contamination in immediate area

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AN-M69 Incendiary Bomblet

Identification

• Designation: AN-M69
• Type: Incendiary bomblet (submunition) -- carried in cluster adapters
• Country of Origin: United States
• Historical Context: Primary weapon of the strategic firebombing campaign against Japan (March 1945 onward)

Physical Characteristics

• Cross Section: Hexagonal (for dense packing in cluster)
• Diameter: 3 inches (76 mm)
• Length: 20 inches (510 mm)
• Weight: ~6 lbs (2.7 kg)
• Fill: Napalm (jellied gasoline)
• Functioning: Timing fuze (3-5 second delay after impact), then black powder charge propels burning napalm up to 100 feet (30 m)
• Delivery: 38 bomblets per E46 cluster adapter; typical B-29 load: 40 clusters = 1,520 bomblets

EOD Hazards -- Aged Condition

• Small size and hexagonal shape: may be mistaken for pipe or structural debris
• Napalm fill: may have polymerized or leaked; residue still potentially flammable
• Black powder propelling charge: may still be functional
• Timing fuze: mechanical timer mechanism in unknown state
• Dropped in enormous quantities (thousands per raid) -- scattered across wide areas
• Many duds: cluster release, timing fuze, and impact all potential failure points
• Found across Japanese home islands, particularly in urban areas of Tokyo, Osaka, Nagoya, Kobe

Historical Context

• March 9-10, 1945: 300+ B-29s dropped ~2,000 tons of M69 clusters on Tokyo, burning 16 square miles
• February-August 1945: Firebombing campaign destroyed major portions of 67 Japanese cities

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US Naval Gunfire Rounds

5"/38 Caliber Naval Shells

Identification

• Designation: 5"/38 caliber Mark 12 gun ammunition
• Type: Naval gun projectile (most-fired US naval round of WW2)
• Caliber: 5 inches (127mm)
• Country of Origin: United States

Physical Characteristics

• Projectile Weight: 55 lbs (25 kg)
• Muzzle Velocity: 2,500 ft/s (762 m/s)
• Shell Types:
  • AA Common (most common): HE fill with mechanical time fuze or VT (proximity) fuze
  • Special Common: Semi-AP with base detonating fuze
  • HC (High Capacity): Maximum explosive fill for shore bombardment
  • Illumination / Star shell
  • WP (White Phosphorus): Smoke/incendiary
• VT Fuze: Radar proximity fuze -- revolutionary technology, made shell 3x more effective than time-fuzed rounds

Scale of Use

• Over 8,000 5"/38 guns produced 1940-1945
• Mounted on virtually every US warship in the Pacific
• Millions of rounds fired in shore bombardment across Pacific campaign

Where Still Found

• Embedded in soil at every Pacific island subjected to naval bombardment
• Okinawa, Iwo Jima, Saipan, Guam, Peleliu, Tarawa -- all received massive 5"/38 bombardment
• Often found at relatively shallow depth (lower velocity shore bombardment rounds)

EOD Hazards -- Aged Condition

• VT (proximity) fuze rounds: contain miniature radar transmitter with battery -- electrical state unknown
• Mechanical time fuze rounds: clockwork mechanism may be partially run
• Base-detonating fuze rounds: fuze at base of shell, difficult to access without moving round
• WP rounds: white phosphorus spontaneously ignites on contact with air -- if casing is breached, WP will burn on exposure
• HE fill: typically TNT or Composition A; standard aging hazards apply
• Driving bands (copper/gilding metal): useful for identification -- resist corrosion better than steel body

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16"/50 Caliber Battleship Shells (Iowa Class)

Identification

• Designation: 16"/50 caliber Mark 7 gun ammunition
• Type: Battleship main battery projectile
• Caliber: 16 inches (406mm)
• Country of Origin: United States

Physical Characteristics

• Mk 8 APC (Armor-Piercing):
  • Weight: 2,700 lbs (1,225 kg)
  • Muzzle Velocity: 2,500 ft/s (762 m/s)
  • Penetration: 20 inches of steel armor or 21 feet of reinforced concrete at 20,000 yards
• Mk 13 HC (High Capacity / Shore Bombardment):
  • Weight: 1,900 lbs (862 kg)
  • Muzzle Velocity: 2,690 ft/s (820 m/s)
  • Crater: 50 feet wide x 20 feet deep
  • Defoliation radius: 400 yards from impact point
• Maximum Range: 24 miles (39 km)

Where Still Found

• Primarily at sites of shore bombardment: Okinawa, Iwo Jima, Philippines
• Deep penetration on impact (particularly AP rounds) means these are found at extreme depth
• Rare as UXO but CATASTROPHIC if encountered

EOD Hazards -- Aged Condition

• Massive explosive fill in HC rounds
• AP rounds: thick forged steel body resists corrosion well; may appear more intact than expected
• Base fuze on AP rounds: large and complex, condition unknown
• ANY 16" UXO find requires maximum evacuation radius and specialized disposal planning
• Deep burial makes excavation extremely hazardous

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US Torpedoes

Mark 13 Aerial Torpedo

Identification

• Designation: Mark 13
• Type: Aerial torpedo (air-launched)
• Country of Origin: United States
• Era: Standard US aerial torpedo throughout Pacific war

Physical Characteristics

• Length: 13 feet (3.96 m)
• Diameter: 22.4 inches (569 mm)
• Total Weight: 2,216 lbs (1,005 kg)
• Warhead: 600 lbs (272 kg) Torpex
• Speed: 33.5 knots (62 km/h)
• Range: 6,300 yards (5,760 m)
• Production: 17,000 produced during the war

Explosive Fill -- Torpex

• Composition: 42% RDX, 40% TNT, 18% aluminum powder
• Significantly more powerful than TNT alone (~50% more blast effect)
• Aluminum powder component: can react with water over decades to produce hydrogen gas

EOD Hazards -- Aged Condition

• Torpex fill: RDX component relatively stable but aluminum powder creates gas generation risk in flooded torpedo
• 600 lbs of explosive -- major disposal operation
• Contact exploder mechanism: may be in partial-arm state
• Found on harbor floors, in reef structures, and in wreck sites
• Initially unreliable weapon (many duds in early war) -- high probability of encountering unexploded specimens from 1942-1943 attacks
• Propulsion section: compressed air + alcohol fuel system

Historical Context

• Early versions extremely unreliable -- had to be dropped at 50 feet altitude, 110 knots
• By late 1944: improved to allow drops from 2,400 feet at 410 knots
• Early-war reliability issues mean MANY unfired or dud torpedoes on Pacific seafloors

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US Mines

M1 Anti-Tank Mine

Identification

• Designation: M1 (and variants M1A1)
• Type: Metallic anti-tank pressure mine
• Country of Origin: United States

Physical Characteristics

• Diameter: 203mm (8 in)
• Total Weight: 4.9 kg (10.8 lbs)
• Body: Circular steel base with cruciform pressure plate
• Explosive Fill: 2.75 kg (6 lbs) cast TNT
• Fuze: Integrated pressure-activated fuze assembly with booster
• Activation Pressure: ~500 lbs on striker head; ~250 lbs on spider rim

EOD Hazards -- Aged Condition

• All-metal construction: heavy corrosion after 80+ years in tropical soil
• Pressure plate mechanism may be corroded in near-fire position
• TNT fill: standard aging hazards
• Often found in defensive positions around former perimeters
• May have been laid in patterns -- where one is found, expect more

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M2 Bounding Antipersonnel Mine

Identification

• Designation: M2
• Type: Bounding fragmentation antipersonnel mine
• Country of Origin: United States

Physical Characteristics

• Body: Cylindrical steel main body containing a 60mm mortar shell body
• Fuze Stand: Tall thin fuze stand with pin-based tripwire fuze or combination pressure-tripwire fuze with pronged pressure cap
• Functioning: Tripwire or pressure activates propelling charge, launching mine body to waist height before detonation

EOD Hazards -- Aged Condition

• Tripwire components long since deteriorated but pressure cap may still function
• Propelling charge may have degraded but 60mm mortar body retains explosive
• Bounding mechanism: spring/propellant in unknown state
• Found at former defensive perimeters
• NOT a successful design (replaced postwar) but still encountered

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US Underwater Demolition Charges

UDT Demolition Charges

Identification

• Designation: Various -- standardized packs and tubes
• Type: Underwater demolition explosive charges
• Country of Origin: United States
• Users: Underwater Demolition Teams (UDTs) -- precursors to Navy SEALs

Physical Characteristics

• Primary Charge: 20-pound rubber tubes of tetryl explosive
• Block Charges: Tetryl blocks wound with primer cord and soft wire, carried in "Schantz pack" (fabric apron with flotation bladders)
• Primer Cord: Detonating cord connecting individual charges to main trunk line
• Typical Operation: Charges emplaced on reef obstacles, connected by primer cord to main trunk line leading to time fuze or electrical detonator

Scale of Use

• 34 UDTs formed by war's end; 21 saw combat
• Used at every major Pacific amphibious assault from Kwajalein onward
• Morotai operation (September 1944): 8+ tons of TNT used in single reef-clearing operation

Where Still Found

• On reef lines at former amphibious assault beaches
• Partially detonated charge remnants on coral obstacles
• Emplaced but unfired charges at operations that were cancelled or redirected
• Primer cord remnants embedded in coral

EOD Hazards -- Aged Condition

• Tetryl: more sensitive than TNT; degrades to form picric acid over time
• Rubber tube casings have deteriorated, exposing tetryl directly to environment
• Primer cord: PETN core may still be functional after decades
• Charges incorporated into coral reef growth -- disturbance of reef may expose explosive
• Underwater environment: saltwater has likely dissolved some charge material but residual tetryl hazardous

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Locations Where WW2 UXO Is Still Found

Japan

Okinawa

• Estimated Remaining: ~1,900 metric tons (as of 2025)
• Historical Load: ~200,000 metric tons of shells fired on main island; ~5% (10,000 metric tons) failed to detonate
• Annual Disposal: 33,527 pieces / 12.9 tons disposed in FY2024 (432 cases)
• At Current Rate: Clearance will take 50-70+ more years
• Types Found: US GP bombs (all sizes), 5"/38 naval shells, 16" battleship shells, mortars, grenades, Japanese defensive ordnance
• Recent Incidents:
  • 2024: Japanese troops disarmed WW2-era bomb in Naha (Okinawa's capital)
  • 2025: American-made bomb found near runway on small Okinawa island
  • March 2025: Explosion during UXO clearance at Okinawa wharf
• Key Concern: Construction and development continuously uncover buried ordnance

Iwo Jima (Ioto) / Ogasawara Islands

• Status: Access restricted; island considered too contaminated for development
• Garrison: JGSDF maintains 400 troops; EOD disposal ongoing
• Types Found: US and Japanese ordnance from one of the most intense bombardments of the war
• Historical Context: 70,000+ rounds of naval ammunition fired at island before and during the 36-day battle

Philippines

• Key Locations: Corregidor, Clark Air Base, Subic Bay, Bataan, Leyte, Manila
• Status: UXO continues to endanger civilians -- 21 documented victim stories at Clark/Subic alone (2011)
• Recent Finds:
  • 105mm projectile found in school compound in Bataan (strong enough to destroy a building)
  • Ongoing discoveries at former Clark Air Base and Subic Naval Base areas
• Types Found: US and Japanese bombs, artillery shells, mortar rounds, grenades, naval ordnance
• Historical Context: Manila was one of the most heavily destroyed cities of WW2 (February-March 1945 battle)

Palau

• Contamination: 10,844 ERW items found since NPA began survey/clearance in 2016
• Historical Load: US forces fired 2,800+ tons of munitions from air and naval vessels on Peleliu alone (1944)
• Key Sites: Peleliu (Marines rebuilding runway on site of 1944 battle), Angaur, Babeldaob
• Clearance: Norwegian People's Aid (NPA) conducting operations since 2016

Guam, Saipan, Tinian, Rota (Mariana Islands)

• Saipan/Tinian/Rota: 2,000-4,000 UXO pieces recovered in late 2018/early 2019 on Saipan alone
• Guam: Ongoing discoveries during construction and agricultural activities
• Historical Context: Mariana Islands campaign (June-August 1944) involved massive naval bombardment and ground combat
• Types Found: US and Japanese ordnance of all types

Papua New Guinea

• Contamination: ~59% of PNG contaminated with explosive remnants of war
• Casualties: Estimated 25,000+ people injured or killed by UXO since 1945
• Key Sites: Rabaul (major Japanese base), Bougainville, Oro Province, Wewak, Lae, Salamaua
• Clearance: HALO Trust began operations in Oro Province and Bougainville in July 2025
• Historical Context: Japanese fortress at Rabaul held 100,000+ troops; bypassed and bombed continuously 1943-1945

Solomon Islands (including Guadalcanal)

• Disposal in 2024: 6,121 UXOs disposed nationwide; 3,200 cleared in Western Province under Operation Render Safe
• 2024 Discovery: 200 unexploded WW2 shells uncovered in Honiara (capital, on Guadalcanal)
• Clearance Operations: Operation Render Safe (multinational -- US, Australia, Canada, New Zealand, RSIPF) -- 20th iteration conducted
• Historical Context: Battle of Guadalcanal (August 1942 - February 1943) -- first major Allied ground offensive in Pacific

Marshall Islands / Gilbert Islands

• Key Sites: Kwajalein, Eniwetok, Tarawa, Makin
• Status: UXO contamination confirmed but systematic clearance limited by remote location and small population
• Historical Context: US amphibious assaults 1943-1944; Tarawa (November 1943) was scene of catastrophic reef-obstacle problem that led to creation of UDTs

China (Japanese Chemical Weapons)

• Scale: 50,000+ chemical munitions found across 90+ sites
• Agents: Mustard gas, lewisite, phosgene, diphenylcyanoarsine
• Disposal: Japan-China joint destruction operations ongoing since 2010 with OPCW support
• Location: Primarily northeastern China (former Manchuria) but scattered across eastern China
• Civilian Casualties: Chemical UXO has injured Chinese civilians decades after the war

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Aged Ordnance Hazards -- General Guidance

Explosive Fill Degradation (80+ Years)

Fuze Degradation

Underwater/Marine Environment Effects

• Corrosion acceleration: Saltwater, temperature, dissolved oxygen, pH all accelerate metal corrosion
• Biofouling: Coral, barnacles, marine growth mask ordnance shape and create false surfaces
• Sediment burial: Wave action and sediment transport can bury then re-expose UXO cyclically
• Explosive leaching: TNT and related compounds dissolve slowly into seawater, creating contamination plume
• Gas generation: Aluminum-containing fills (Torpex) generate hydrogen gas in flooded casings; pressure buildup possible
• Casing breach: Marine corrosion eventually breaches all steel casings; explosive fill directly exposed to environment
• Temperature cycling: Tropical shallow water temperature variations stress corroded casings

General Rules for WW2 Pacific UXO

1. Assume maximum sensitivity -- aging makes ordnance MORE dangerous, not less
2. Picric acid kills -- any Japanese ordnance with picric acid fill has formed metal picrates; treat as primary explosive sensitivity
3. Mercury fulminate detonators -- present in many Japanese fuzes; extremely shock-sensitive after 80 years
4. Chemical weapons possible -- Japanese chemical fills found across China and Pacific; always consider CW hazard
5. Fuze condition unknown -- no fuze on any 80-year-old item can be assumed safe
6. Cluster munitions scatter -- where one bomblet is found, expect dozens more
7. Coral incorporation -- items may be encased in coral growth; reef disturbance can expose UXO
8. Multiple nationalities -- at most Pacific sites, BOTH US and Japanese ordnance are present
9. Do not rely on markings -- paint, stencils, and stampings are obliterated by corrosion; rely on dimensional/shape identification
10. White phosphorus -- US WP rounds spontaneously ignite when casing is breached and WP contacts air

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Sources