Battle of Amami-Ōshima

This December 2001 “battle,” described as a six hour firefight, between a small North Korea (NK) vessel and four Japanese Coast Guard cutters was unusual, but it is interesting for what it can tell us about the difficulties of dealing with a vessel that refuses to stop, as would probably be the case with a terrorist attack.

The incident happened outside Japanese territorial waters but inside their EEZ.

The NK vessel appeared to be a trawler, but this was no trawler. It was reportedly capable of 33 knots.

The Japanese went through the usual procedures trying to get the vessel to stop, flags, loud hailer, warning shots. When these were ignored, at least initially the Japanese apparently chose an aim point forward in the vessel where it was unlikely to hit crew members. Over 1000 shots were fired.

As appears to be standard procedure with the Japanese Coast Guard, it was not a single cutter, but a team of cutters that responded. In this case four. Japan Coast Guard aircraft were on scene, but apparently they had no airborne use of force capability.

Generally in the video, it appears that the cutters remained abaft the beam of the target vessel, minimizing the pursued vessels opportunity to ram a cutter and also insuring that friendly vessels were not in the line of fire.

Tsurugi class cutter PS202 Hotaka. From Wikipedia commons.

The Japanese cutters seen in the video appear to be Tsurugi class “high speed special patrol ships” specifically designed to intercept high speed North Korean vessels engaged in espionage or smuggling. They are longer but lighter than the Webber class, 50 meters (164 feet) in length with a 220 ton full load displacement and three diesels totaling

15,000 HP through three water jets. They are reportedly capable of 50 knots (other sources indicate 40 knots) and are armed with a JM61 20 mm Gatling gun, the Japanese version of the same gun that arms the Phalanx close in weapon system (CIWS). These might be thought of as similar to my proposal for a WPB replacement, Response boat, large–interceptor.

After the North Korean vessel was disabled the cutters came close aboard (about time 6:30). The wisdom of this was questionable since the vessel had been firing at the cutters. In fact the nearby cutter was fired upon. Subsequently apparently the crew of the NK vessel detonated scuttling charges, which had they been larger, might have damaged a nearby cutter.

15 survivors were seen after the sinking, but the cutters were told to ignore them as there was fear they would respond to rescue attempts with suicidal violence. The Japan CG cutter crews were relatively small. All members of the N. Korean crew were lost. Only three bodies were recovered.

The North Korean vessel was small, 29.7 meters (97.4 feet) in length, but still the weapons used against it were found wanting. Due to the presence of heavy weapons like RPGs, recoilless rifles, and MANPADs on N. Korea spy vessels, the Japanese concluded that the 20mm Gatling gun was not adequate for their purposes and now expect to include vessels with 40mm guns in any similar future operation.

As I have noted before, I believe all Coast Guard vessels, WPB and larger, should be armed to forcibly stop any vessel regardless of size and have an effective range of at least 4,000 yards, so as to be outside the effective range of most potential improvised vessel weapon systems.

The North Korean vessel was subsequently raised to allow investigation of the incident. The vessel and some of its contents are on display at the Japan Coast Guard museum in Yokohama (see below).

A steel helmet and parts of a Soviet B-10 recoilless rifle.

ZPU-2 14.5mm anti-aircraft gun found on the North Korean spy trawler sunk by the Japanese Coast Guard in 2001. Transferred from ja.Wikipedia; ja:Image:North-Korea spy-vessel 2.jpg, Author: Bakkai at Japanese Wikipedia

Weapons including RPGs and automatic weapons found when the North Korean vessel was raised. Author: Nomansland511 (a.k.a. nattou)

North-Korean Spy Vessel Rear View, showing boat hangar in stern. Author: nattou

North-Korean Spy Vessel in Japan Coast Guard Yokohama Base, Kanagawa, Japan. Author: nattou

20 thoughts on “Battle of Amami-Ōshima

  1. It is interesting what drives requirements for armament. Our latest B2 Rivers will go to sea with 30mm Bushmasters and simple installation at that. The German Federal Polic’s new cutters the Potsdam class will go to sea with a BAE 57mm. Why do we think we only need a small simple gun? And why do the Germans think they need a modern 57mm? Which is right? I don’t know.

    • That is an interesting comparison, that I find strange, because the German operators are “police” and the British operators are Royal Navy. My own perspective is that we need a gun as a signaling device. Then over and above that, we need a weapon than can forcibly stop any vessel, regardless of its size.

      • I don’t think many who comment on naval matters realise how useless the gun is as a weapon against other vessels. And as you often point out especially for ‘mission kill’. The only exception to that might be heat seeking PGM delivered from a gun. The Italians have a wonderful CGI video on YT which shows such rounds finding their way down the uptakes of an enemy ship.

        We Brits don’t really take our maritime border security seriously. We have a hand full of Rivers and the Border Agency cutters number 4/5 and a hand full of recently purchased large RHIBs with cabins. Compare that with say Germany who have 4 (approximately the numbers are changing as the Potsdown come into service) “police ships”, 8 good sized custom cutters (two are 1000 tonne SWATHs), and then the coastal states have their own water police units. France has more hulls patrolling the Bay of Biscay than we do our whole coast. My favourite maritime law enforcement agency is the Italian customs service. They have so many assets afloat the service has its own training ship……..

      • @x, Speaking of the Guardia di Finanza, I just saw this from Defense Industry Daily. That they had ordered 22 new helicopters. They have almost as many helicopters as the Coast Guard. Some pretty impressive, very fast, patrol boats. Most of Italy’s borders are maritime and there is a lot of potential smuggling in the Mediterranean. Their organization relative to the armed forces does sound a lot like the USCG.

        The Italian Army has placed an order with Leonardo for 15 AW169 helicopters. This is the second successful sale of the military variant. Italy’s Guardia di Finanza police agency was the first to order this variant back in 2018 with an order for 22. The procurement, disclosed by the country’s Ministry of Defense solidifies an earlier announcement made in January that the AW169M was to be bought to replace the army’s Bell AB 205, AB 212, and AB 412 LUHs, and to augment its Boeing CH-47F Chinook, NHIndustries NH90, AgustaWestland A129 helicopters. According to the procurement document, the deal with Leonardo, which is valued at $301 million, comprises delivery of two helicopters in a ‘commercial basic trainer’ configuration, as well as approval for the start of development of 15 new ‘advanced multirole’ configuration helicopters for the Italian Army.

  2. In this particular engagement, the Japanese were probably trying to stop the Korean vessel more than sink it. The intelligence gained by being able to examine the Korean vessel being invaluable.

    The principle problem the Japanese faced in this engagement was range. They could not bring their weapons to bare without putting themselves at risk.

    This is something Chuck mentions from time to time and it is a real issue. It’s also fairly easily mitigated as there are many suitable weapons available that would give Coast Guard vessels great standoff range as well as more stopping power.

    I personally like moving to the 57mm on most of our assets as it’s already in inventory and thus a known commodity. With the new rounds being developed for it, it should be pretty formidable in dealing with small threats.

    It also would not upset the applecart, allowing the CG to avoid taking on the training, chain of command and other issues associated with missiles.

    The will and vision have to be there however and I don’t think it will be until there is an unfortunate incident.

  3. The security mosaic for the Italians is interesting. My point is between the Guardia di Finanza and say the Germany’s Küstenwache des Bundes and Wasserschutzpolize you can see that we Brits are somewhat lacking. We might be an island on the edge of Europe but consider that the Irish established a marine unit for their customs service because of the problems of illegal landings mostly from the Netherlands. Our borders are open. The Finnish border guard has a huge number of boats. All countries are different and have different needs. But the UK is not unique.

  4. If you are going to fire warning shot “across the bow” from a distance where the cutter is relatively safe (about 4000 yards), you need a pretty capable weapon and fire control system–definitely something bigger than 25mm.

    • Larger calibers may be more effective, but they do more than disable. They potentially will destroy small targets. The benefit of 25mm, 30mm and maybe 35mm guns is that they are more likely aimed at a particular point, but don’t carry as much explosive power, thereby allowing a disabling instead of destroying effect.

      • @X, The Coast Guard had a couple of ships of the same class, 143 foot tugs. Former USN ATAs. USCGC Modoc and Comanche. Thought it remarkable that this little ship survived. Does show how hard it is to sink a ship or even get a mobility kill.

      • @DaSaint, regardless of the size of the gun, you don’t have to fire explosive projectiles. In fact non-explosive projectiles may be better for disabling fire.

        For warning shots across the bow, you want the gun to make a lot of noise and the projectile to make a big splash, but you don’t want it to explode because shrapnel might hit the vessel you are trying to signal to stop.

        As for disabling fire, we have a huge potential range of targets. For larger targets heavy machine guns may not be effective. Large marine diesels are very robust. I think at one point I calculated that the explosions regularly going off in the cylinders of a large marine diesel were more energetic that the explosion of a 57mm projectile.

        If the projectile explodes after penetrating the hull at the engine room, before hittig the engine itself, unless a fragment cuts an oil or fuel line or some other critical piece of auxiliary equipment, it is unlikely to stop the engine. An armor piercing round, particularly a discarding sabot round may be a better choice.

        For the vessels that are most likely to be available to confront a terrorist vessels, WPBs and WPCs, a 57mm is probably the largest gun we could expect to be fitted. 76mm guns are sometimes fitted to vessels of this size, but since the USN is no longer using 76mm we could not expect any more installations.

        Unfortunately there are currently no armor piercing discarding sabot rounds for the 57mm.

        We did earlier discuss the possibility of mounting a 40 or 50mm gun.


        and here:

  5. The 57mm is not perfect due to the lack of a purpose built deep penetrator. It has the huge advantage of already being in inventory though.

    I can’t see the CG adopting a gun not already in use by the USN.

    The Coast Guard may though, sponsor the development and production of a deeper penetrating 57mm round. The more 57mm guns used by the CG, the more this makes sense.

    • Yes I would not expect to see any weapon adapted by the Coast Guard unless it was in the Navy inventory. It appears that may still be possible for the 40 or 50mm chain gun. But its not going to happen real soon.

  6. The penetration of unstable, fragmenting 5.45mm rounds through/into the bridge of the Japanese CG tells the real story. A combination of velocity and Sectional Density of the projectile will sometimes produce unexpected penetration. This has two implications: 1. Are realistic armor specs being applied to CG’s vessels? (rhetorical, naturally, since this is classified), and 2. What can be done with what we have (like SLAP rounds for the 25mm)??

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