World War II

Similar to other underwater weapons, the Japanese did not spend much energy on mines prior to World War II. This was mainly because mines were considered to be "defensive" weapons and so were not of value to an "offensive" minded Navy.

Almost all Japanese mines were of Hertz Horn construction. No magnetic (influence) mines were developed although a number of British A Mark I - IV mines captured at Singapore were laid off Balikapan in 1945. A shore-controlled mine with an acoustic detector was developed late in 1944 and 144 were laid across the entrance to Tokyo Bay.

Triggering or Fuzes

As mentioned above, the Japanese used Hertz Horns almost exclusively. Each horn contained acid. Contact with the horn broke open the acid container which energized a battery and exploded the mine.

During the war a variation was developed that replaced the acid horns with switches that activated when a ship hit the horn. By definition, horned mines were short ranged weapons and fields needed to be densely packed to be effective against shipping.

Explosives

The Japanese used a variety of explosives in their mines.

Name Composition
Shimose Picric Acid
Type 88 66% ammonium perchlorate, 16% ferro-silicon, 12% wood pulp, 6% oil. It was believed that silicon carbide assisted in the uniform propagation of a detonation wave through loosely packed powder.
Type 97 60% TNT, 40% hexanitrodiphenylamine (HND).
Type 98 70% trinitroanisole, 30% HND.
Type 1 81% ammonium picrate, 16% aluminum, 2% wood pulp, 1% oil.

Effectiveness

Unknown. I would appreciate any information in this regards.

Moored Contact Mines

Shimose 5 Mod 1

Total Mass 1,146 lbs. (520 kg)
Explosive Charge 183 lbs. (83 kg)
Trigger/Fuze 4 Hertz Horns

Mark 6 Model 1

Total Mass 2,549 lbs. (1,156 kg)
Explosive Charge 474 lbs. (215 kg) Shimose
Trigger/Fuze 4 Hertz Horns

Mark 6 Model 2 and Mod 1

Total Mass 2,381 lbs. (1,080 kg)
Explosive Charge 441 lbs. (200 kg) Shimose
Trigger/Fuze 4 Hertz Horns

Mark 6 Model 3

Total Mass 1,984 lbs. (900 kg)
Explosive Charge 441 lbs. (200 kg) Shimose
Trigger/Fuze 6 Hertz Horns

Type 88 Mod 1

Total Mass 2,116 lbs. (960 kg)
Explosive Charge 397 lbs. (180 kg) Shimose
Trigger/Fuze 4 Hertz Horns

Type 93 Model 1

Total Mass 1,543 lbs. (700 kg)
Explosive Charge 220 lbs. (100 kg) Type 88
Trigger/Fuze 4 Hertz Horns

Type 93 Model 2

Total Mass 1,543 lbs. (700 kg)
Explosive Charge 220 lbs. (100 kg) Type 88
Trigger/Fuze 7 Hertz Horns

Type 93 Model 3

Total Mass 1,543 lbs. (700 kg)
Explosive Charge 220 lbs. (100 kg) Type 88
Trigger/Fuze 9 Hertz Horns

Type 93 Model 4

Total Mass 1,565 lbs. (710 kg)
Explosive Charge 243 lbs. (110 kg) Type 1
Trigger/Fuze 4 Hertz Horns

Type 4

Total Mass N/A
Explosive Charge 88 lbs. (40 kg) Type 88 or Type 1
Trigger/Fuze Hertz Horns; 3

Type 5

Total Mass N/A
Explosive Charge 88 lbs. (40 kg) Type 1
Trigger/Fuze Hertz Horns; 3

"Small Beach"

Total Mass N/A
Explosive Charge 88 lbs. (40 kg) Type 88 or Type 1
Trigger/Fuze 4 Hertz Horns

Aircraft Type 3 Mark 1 Model 1

Total Mass 1,411 lbs. (640 kg)
Explosive Charge 176 lbs. (80 kg) Type 97
Trigger/Fuze 4 Hertz Horns

Deployed using a parachute.

Other Mines

Aircraft Type 3 Mark 2 Model 1

Total Mass 298 lbs. (135 kg)
Explosive Charge 110 lbs. (50 kg) Type 97
Trigger/Fuze Switch horns; 3

Drifting mine. Deployed using a parachute.

Type 96 Mod 1

Total Mass 238 lbs. (108 kg)
Explosive Charge 121 lbs. (55 kg) Type 88

Attached to anti-submarine nets. Fired when the tension on the net exceeded a set value.

Type 92

Total Mass 2,866 lbs. (1,300 kg)
Explosive Charge 1,102 lbs. (500 kg) Type 88

A shore-controlled acoustic mine.

Type 92 Model 1

Identical to the Type 92 but without acoustic detector.

Post-World War II

Japan currently uses mines either identical to, or externally similar to, USA types. They are designated in a K series during their development cycle, after which they receive type numbers.

K-15/Type 56

A moored antenna mine, similar to the USA Mark 6.

K-21, K-22, K-23 and K-24/Type 70

Bottom magnetic (influence) mines similar to the USA Mark 36.

K-33

Moored contact mine, similar to World War II types.

Type 55

Moored contact mine, weight 1,565 lbs. (710 kg), TNT charge of 220 lbs. (100 kg), uses 7 Hertz Horns.

Sources

Data from:

  • "Naval Weapons of World War Two" by John Campbell
  • "US Naval Weapons" and "The Naval Institute Guide to World Naval Weapon Systems 1991/92" both by Norman Friedman