This is the third in a series comparing two incidents from World War II, in which ships tried to force entry into a hostile harbor, in an effort to draw some lessons from them. Part one looked at the bloody, but ultimately successful British assault on the fortified port of St Nazaire. The second was the unsuccessful attempt by heavy units of the German Navy to reach Oslo, Norway, thwarted by an obsolete and undermanned fixed fortification. What went wrong? And what went right? What can we learn?

In an ideal defense there would be early positive identification of threats. There should be no possibility of mistakenly engaging a non-threat. There would be adequate time to make a decision. And the weapons would be so effective that even if things went wrong, and the threat wasn’t recognized until the last possible moment, we could be confident that the weapons would succeed in  stopping the threat. In addition we want confidence the weapons will not cause unintended collateral damage.

In the case of the German Defense of St Nazaire, it appeared that they had adequate resources. The heavy artillery should have been able to destroy such a small ship, but

• There was a report (by the U-boat) of enemy ships in the area, but instead of locating them and attacking or trailing them, they made a comfortable assumption that they had left the area.
• They had “defense in depth,” but the reach of their weapons exceeded the reach of their detection. Heavy weapons were sited to repel a conventional large scale attack at a distance. Their guard ship was relatively close to the target.  Cambeltown’s attack was not recognized until after she had passed the firing arcs of the heaviest guns. The heavy guns were not sited so that they could hit even if the recognition of the threat was late. (You have to expect that things will not work as planned.) The same sort of problem could result because some weapons have a significant minimum range.
• They did not seem to recognize that there were circumstances when an attack could be made by approaching from outside the dredged channel. (Environmental changes matter, tide, phase of the moon, tidal currents all effect the enemy’s options and can change surveillance requirements.)
• Surveillance was not  adequate to identify the threat early enough to allow a decision when the heavy guns could hit. The first report of suspicious activity was only 24 minutes before the Cambeltown rammed the dock gates, and a determination that an attack was underway came only six or seven minutes before the destroyer rammed the gates. Cambeltown was allowed to continue toward the target essentially unengaged for the 17 or 18 minutes from detection to the decision to engage.
• Campbeltown gained five minutes by using deceptive signals and all the while she was getting closer to her target. Procedures were not in place that would have required the positive identification of an approaching vessel while it was still in the kill zone and destruction of any that had not complied.
• The weapons that they did have, that would bear during the last few minutes, 75 mm guns and 20 to 40 mm automatic cannon, caused a lot of casualties, and were effective against small craft, but ultimately could not stop the ship.

The Norwegian planning was simple, straight forward and effective going back more than 40 years.

• They had the advantage of a restricted approach and made good use of the geography.
• The threat was challenged by both a guardship and a fort further down the fjord so that in spite of otherwise poor communication, Oscarborg Fortress had time to make the best use of their inadequate personnel.
• They did not have “defense in depth.” They failed to deploy their minefield, but the weapons they did have, had a high probability of success. (Redundancy is a good thing.)
• The Commander at Oscarborg violated his ROE by not firing warning shots, but the two previous contacts by the guardship (POL III) and the Oslo fjord fortress further down the fjord gave him confidence he was doing the right thing.
• The weapons were sited where their obsolete technology made little difference.
• From the time the Fortress opened fire, to the time they launched their torpedoes was 9 minutes, the interval would probably have been shorter if the cruiser had not been going so slow.
• Even the two 11″ gun hits did not stop the Blucher’s advance up the fjord, although given the distance they ultimately might have.
• The torpedoes in spite of their age were effective ship stoppers.

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If the attack on the USS Cole in 2000, wasn’t sufficient, at least since 9/11, the possibility of a maritime terrorist attack has been a concern for the Coast Guard. The Mumbai attack, which came by sea in 2008, should have reinforced that concern (here). I am particularly concerned that we may not prepared to deal with an attack if it is staged using a ship of any significant size. The weight of weapons required to stop a ship is not generally appreciated. Even the 76 mm and 57 mm guns on our largest cutters are relatively light weapons in terms of stopping ships, similar to the 20 mm to 75 mm guns that failed to stop the Campbeltown, even though she displaced only a little over 1,000 tons.

We might like to assume that we will be able to call on our sister services if we need heavy weapons, but that expectation is not realistic unless there is a prior commitment, communications systems in place and practiced, and assets armed and on alert. Getting support from other armed services is not likely to happen. In the US, they don’t have vessels or aircraft standing by, loaded for anti-surface warfare, and they don’t have duty officers with the authority to launch strike capable assets.

Even if we had prior commitments, two questions remain. Will the response be adequate? and, can it avoid collateral damage in the surrounding area?

What will be effective depends a great deal on the time dimension. How much notice are you going to get? If it is ample, several hours, a lot of alternative open up, but if it is less than an hour, and probably less than 30 minutes, as I believe it will be, then “Its run what you brung.”

Time effects our own effectiveness as well as our ability to bring in other services. Say we identify the threat well off shore and engage it with a National Security Cutter. They refuse to surrender and we empty our magazines into the the ship. We get 200 hits. At about 6 pounds per shell that is 1200 pounds of ordnance on target. That is a little more shell weight than the two 11″ shells that hit the Blucker. Ultimately fire and progressive flooding may sink the ship, but it will probably take hours, perhaps days before it sinks. If we are lucky, it will have stopped the ship, but past experience indicates it may not.

If the ship is less than an hour from its target, if we are trying to chase it up a narrow channel, even 200 hits from the 57 mm may not do the job.

If we are chasing it up a narrow channel, with civilians on either side of the estuary, do we really want to be expending massive amounts of ammunition. With all due respect to our gunners mates, some are going to miss or pass through the ship and continue on to impact in areas we never intended.

Potential Targets (examples only, there are others):

SAN DIEGO: It is only about 9 miles from Mexican waters to the entrance to San Diego harbor. A ship transiting close to the shore going North from Mexico is easily explained as a transit to Canada. There are a number of targets that might interest terrorists. Less than two miles inside the harbor entrance there is the submarine base. Just over five miles in, there is the city center on one side of the harbor and North Island with its carrier moorings on the other. A little further the bridge to Coronado, and beyond that the Naval Base.

I would think a terrorist most likely to attack a carrier as a “symbol of American power and arrogance.” An attack on a ship at the pier, they might include landing a small force to shoot up the Exchange and Commissary.

Its not hard to determine when major ships will be transiting the channel, as when Carrier Strike Groups go on Deployment, so there are also opportunities to intentionally collide and detonate a charge, possibly in the form of a massive shaped charge, while a carrier is in the channel.

It could be only an hour’s transit time from Mexican Waters to the carrier. Not much time to recognize a problem, formulate a course of action, and get it implemented.

NORFOLK: It is only a bit over 10 miles from the Chesapeake Bay Bridge tunnel to the Naval Base in Norfolk. Not as accessible as San Diego, but lots of targets there too.

KINGSBAY: It is less than 10 nautical miles from the seaward end of the jetty to the Ballistic Missile Submarine moorings. On Google Earth it looks like there is a barrier preventing access to the access to the moorings for the submarines, but are we confident that it can resist the impact of a ship? There is also the possibility of putting suicide teams ashore short of the barrier to attack the facilities and the subs at their moorings. Even if they ultimately accomplished very little in real terms, the impact on the US public perception of the safety of Nuclear weapons in the US and the propaganda value to our adversaries would be immense.

SAN ONOFRE NUCLEAR POWER GENERATING STATION: This facility is right on the pacific coast. Only 60 nautical miles north of the Mexican border.

STATUE OF LIBERTY: It is only about 7 nautical miles from abeam Sandy Hook to the Verrazano-Narrows Bridge and another five miles to the Statue of Liberty, less than an hour. (To see what the harbor defenses of New York used to look like, check this out.)

Opening the Decision Space:

If we have time to decide to activate a harbor defense organization, the ” Domain Awareness” effort will certainly help and speed innocent vessels though the “vetting” process, but there will always be exceptions that need to be boarded for confirmation. One or more guardships are probably necessary and vessels that have not been administratively cleared need to be directed to wait in a holding area well away from potential targets.  During wartime it may be dangerous to have the holding area outside the harbor, but if the threat is terrorism, it’s an option.

The Weapon of Choice:

The ideal weapon would of course be light, inexpensive, and ubiquitous. But more importantly it should give a high confidence of stopping the attacking ship, even if the decision to employ it is delayed. This gives the commander the maximum decision space, minimizing time pressures to engage what might be an innocent. We need a weapon that can be used in a harbor, without endangering the surrounding population.

The only weapon I see that meets that criteria is a homing torpedo. And it need not be a large torpedo, if it can go after the ship’s propellers. Reprogramming obsolete ASW torpedoes like the Mk 46 torpedo now being replaced by the Mk54 or the even older Mk 44, seems a cost effective solution. Their warhead of less than 100 pounds may not sink a large ship but the technology to make them hit the propeller(s) has been around for since the middle of World War II and modern processors have only made them more reliable.

We would not need a large cutter with a 57 or 76 mm gun to stop a ship (not a good choice in my mind anyway). These torpedoes can be launched from craft as small as WPBs although I would expect if we had such a weapon they would be mounted on Webber class first. The Webbers will be numerous enough to to cover the targets, faster most of our other assets, and yet will have crews with more depth of experience than our WPBs.  These torpedoes are only eight and a half feet long and weighs about 500 pounds, far smaller than the 20 foot long, 2,500 pound weapons that were carried by 78 and 80 foot long PT Boats during WWII.

If we mount them permanently, even if we were not able to activate a harbor defense organization, if the threat developed, we would have an option.

Photo from Wikipedia

(Note: The usual assumption would be that they would be mounted like the torpedo tubes on the PTs, but pointing aft over the transom is also an option that has been used in the past.)