In my previous post, I noted how the the report from international team that investigated the Cheonan sinking noted and dismissed most of the alternative theories about what destroyed the South Korean warship.  However, I did not cover what has emerged as the most popular alternative theory: that the Cheonan hit a mine.  The report deals with the mine theory on pages 83 to 88 (click on first PDF file here to see those pages).

Unlike the other alternatives theories, visual inspection can not dismiss the possibility that the Cheonan was destroyed in an encounter with a mine (page 85 of the report):

As addressed in the surface explosion investigation and analysis result, explosion observations of ROKS Cheonan correspond to a classic case of hull separation due to a shockwave and bubble effect generated by an underwater explosion. Therefore, there is no possibility of contact explosion by surface or moored mine. Although non-contact underwater explosion of moored mine cannot be excluded considering the damage patterns observed, the operable environment of moored mine was severely limited, and with extreme vulnerability of moored mine to be affected in the underwater environment, its employment was assessed highly unlikely.

Let’s break that down:

  • The damage to the Cheonan is not consistent with a contact explosion.
  • The damage to the Cheonan is consistant with a non-contact explosion and there are mines of that type, however…
  • The seas where the Cheonan was sunk do not lend themselves to mine deployment.

Clearly, that last bit requires some justification.

We first must step back and remember that there are three types of mines that can be deployed; moored (in which a floating mine in anchored to the sea bed with a cable), bottom (in which the mine sits on the sea bed, and floating (which, as the name implies, just drifts with tides and currents).

The report concludes on page 86 that conditions in the West (Yellow) Sea where the Cheonan was sunk make the deployment of moored mines nearly impossible:

Therefore, since strong current (3~5kts) and depth (47m), as well as large tide differences (max 4m) and wave height(2.5m) pose significant challenges to moored mine fixationand optimum depth maintenance, employment of moored mine would have beenhighly unlikely.

In other words, there were too many variables in that area to properly calabrate a moored mine.

 

The report also notes that any mine deployed in that area would have had to have missed many targets to hit the Cheonan at that particular time:

 

In the vicinity of Baekryong Island, the industry concentrates its activities during the blue crab season from August to October as well as the blue crab and san eel season from April to June. Even during the slack season from November to March, 40~50 fishing vessels per day engage in fishing.  Moreover, after examining ROKS Cheonan’s track on the day of the incident, it was found that it departed from Daechung Island base at 06:00, March 26th, entered its patrol area at 08:30 and conducted its patrol operation in a zig-zag manner irregularly once or twice per hour in the identical region, thus resulting in patrol near the incident site at least more than 10 times(At the time of the incident ROKS Cheonan was moving in 327°, 6.7kts).  This indicates that there were no prior mine installations.

I am a little underwhelmed by this section.  The Cheonan was destroyed in late March, between the area’s two major fishing seasons.  The Cheonan’s earlier movements in the same are a little more convincing.  However, the irregular pattern of the Cheonan’s movements would seem to me to make it likely that it moved over particular areas that it previously had not during the patrol.

This next section shows a lack of ‘outside the box’ thinking in my view:

 

 

 

In addition, the operational installation of a single mine results in a very low success rate; therefore, multiple number of mines should be laid at the same time in order to raise the possibility of success. However, no mines have been discovered. There are numerous surface vessels such as fishing and merchant vessels operating in the vicinity of Baekryong Island. Targeting a warship would result in a very low likelihood of success.

That passage assumes that a warship was the target and that any mine would have been deployed in a militarily effective fashion.  However, I think any mine deployed by the North Koreans in that area would have been meant to be a weapon of terror rather than a weapon of war.  The goal of placing a bottom or floating mine would have been to hit a random South Korean target in an area claimed by North Korea.

Most of the West Sea off the coast of Korea in that area is south of the Northern Limit Line (NLL), the de facto maritime border between the Koreas established by the UN command at the end of Korean War.  North Korea has never recognized the NLL and the area has been the seen of several military confrontations between the Koreas, most of which turned out badly for the North.  North Korea announced early this year that it would periodically conduct live fire exercises with shore-based artillery batteries firing into waters it claims in the West Sea.  So far, all rounds fired in those exercises have landed north of the NLL but the intend is clear: to frighten South Korean vessels away from the area.

A single mine could be deployed for the same reason: To scare other South Korean ships from the area and turn the seas south of the NNL into a no-man’s land (or no-man’s sea in this case).

So we can be confident that no moored mines were deployed in the area but I think that the possiblity that another type of mine could have destroyed the Cheonan is still viable.