How well do we really trust the French?

January 6, 2008 12:26 PM

What is the policy of the British M.O.D. regarding the Channel Tunnel in case of war in continental Europe?

Anyone know anything about this? I've been reading about Victorian plans for a Channel Tunnel, and how they were all shot down as unsafe given the risk of war. Obviously such a war is all but impossible nowadays, but I'm sure someone somewhere has thought about this. Particularly as the tunnel was planned before the end of the Cold War when Russian tanks were just a few hundred miles from Paris.
Would the tunnel be blown up, throwing away the billions it took to build? I've heard every bridge into Switzerland is mined just to be on the safe side, is there a similar system at work here? Or would they just put a big gun in Dover?

posted by greytape to travel & transportation (14 comments total)

I don't think that invasion via the chunnel is much of a risk these days. If someone's sneaking in, there's any number of ways in -- and if they're coming in force, the chunnel is the least useful way (they'd be sitting ducks the whole time they're in there and would have no element of surprise -- they could complete an airstrike and be home again in the time it takes them to drive the chunnel).

If it looks like the island of Great Britain is going to be lost to the enemy, then maybe you want to blow up the chunnel to disrupt their supply routes.
posted by winston at 12:32 PM on January 6, 2008

General Staffs spend much of their time coming up with war plans for any number of weird circumstances, so there's probably a dusty document on a shelf somewhere, perhaps next to the one detailing how to defend York against an attacking Scottish army. To some extent, these are planning exercises, and the details aren't really meant to be released to the general public, for a variety of political/PR reasons, i.e., I'm sure the US Army has plans to invade Canada lying around somewhere, but no one takes this seriously and all sorts of people would freak out and believe that the US is preparing an imminent invasion of Canada.

Chunnel defense plans are probably in a similar category: planning exercises filed someplace, which would cause more trouble than it would be worth to talk about.
posted by chengjih at 1:06 PM on January 6, 2008

I'm sure the US Army has plans to invade Canada lying around somewhere, but no one takes this seriously and all sorts of people would freak out and believe that the US is preparing an imminent invasion of Canada.

For an example of this, see War Plan Red.
posted by Johnny Assay at 1:28 PM on January 6, 2008

wow cheng, that was a stupendously unhelpful answer.

wikipedia has this:

"1955 Britain ceases its opposition to a Channel Tunnel on military grounds"

which makes sense since in the age of supersonic fighters and terrain-following cruise missiles the island is no longer protected by the Channel, as it was in the crisis of 1940-41.

Found this, fwiw:

"Security arrangements for the Channel tunnel considered under the government of Edward Heath envisaged using a small nuclear device to seal its entrance in the event of war. The recommendation is contained in an exchange of secret memorandums and letters between senior Whitehall officials in the weeks leading to Mr Heath's election defeat in February 1974. "

Military concerns are dismissed offhandedly in 1919 Sunday NY Times piece.

Even a cursory glance through the channel tunnel history shows that popular fear of invasion was a dominant theme from earliest times. . . . here's Gladstone's speech to the House in 1888.

It is an interesting question and unfortunately my google-fu has found its limit. I suspect there are pragmatic measures to render the tunnel unusable, but these would be highly sensitive and not publicised.
posted by panamax at 1:51 PM on January 6, 2008

It would be extremely easy to seal either end of the Chunnel, by any of a dozen means (including air strikes and missiles). Which in turn implies that any halfway competent opponent wouldn't try to use the Chunnel as a major invasion or supply route.

Which in practice means it isn't very important in terms of military planning. The Brits wouldn't use it logistically if they were fighting on the continent, and in terms of defense about the only thing needed would be to make sure two or three reliable means existed for bringing a section of the tunnel down, in case an opponent were stupid enough to try to use it.

The Chunnel is simply too vulnerable, as well as too low capacity, to be militarily important.
posted by Steven C. Den Beste at 2:55 PM on January 6, 2008

If you still had access to your end of the Chunnel and thought it needed to be destroyed, you'd place a couple of tons of explosive about 400 yards into the thing and set it off.

If you didn't control your end, the preferred weapon would be a burrowing bomb, something akin to the GBU-28. You wouldn't aim for the entrance, you'd drop it maybe half a mile from there back along the tunnel and collapse a big section of it.

The result would be unrepairable in any militarily reasonable amount of time.

The British military has been wrecking tunnels for a long, long time. They know all about it.
posted by Steven C. Den Beste at 3:01 PM on January 6, 2008

The Chunnel is simply too vulnerable, as well as too low capacity

Would have been handy for the BEF in WW I, and for supplying the allied bridge-head in WW II, at least in 1940.

In an Operation Seelöwe WW II scenario, it would have been used as much as possible by the invading Germans. Taking a boat trip across the channel wasn't a picnic in 1941, either.

The capacity of a working pair of train lines between the English and French grids is nothing to scoff at, considering how difficult it is these days for a cargo ship to remain above the waves in littoral waters.

From what I can surmise, the only way to put the tunnel out of commission would be to flood the thing, but even then it would be reasonably useful should a cargo submarine be adapted for use to shuttle materiel from the continent.

But yeah, in any credible invasion scenario I can think of, Britain will face a lot greater problems than the Folkestone tunnelhead, should a hostile power be in control of France's Channel coast again.

But it would certainly be something for the MOD to plan against and I'm sure there's something -- like the exposives you suggest above -- out there that details these plans.
posted by panamax at 3:26 PM on January 6, 2008

To answer your question you have to reflect upon Britain and France being partners in NATO and the EU. I'm sure the protection of Britain and how it relates to the Channel, Chunnel, Air, Continent, Atlantic, Arctic and Hemisphere have all been accounted for by MOD in a rather detailed manner, but I'm also sure that those plans are prefixed by some sort of likelihood report so that they don't have egg on their face if the wrong person ever gets wind of it.
posted by furtive at 4:04 PM on January 6, 2008

Crap, I misunderstood your intent, I thought you meant plans in the event of war with the European continent.
posted by furtive at 4:05 PM on January 6, 2008

I think it would quite easy to block the tunnel without necessarily flooding it--just place a few charges in the right places and it would be easily blocked. If desperate and you want to make sure, blow up a small nuke and make it so the thing would have to be completely rebuilt/retunneled.

If the charges/nuke does cause the tunnel to flood that's a bonus.
posted by aerotive at 4:49 PM on January 6, 2008

They could arrange an engine fire in a small family car; that closes it for weeks.
posted by bonaldi at 6:24 PM on January 6, 2008 [1 favorite]

From what I can surmise, the only way to put the tunnel out of commission would be to flood the thing...

Not correct. The way to put the tunnel out of commission is to collapse a couple hundred yards of it. Which can easily be done with conventional explosives, and it doesn't necessarily even take all that much. Military engineers have long experience doing such things.

Tunnels are like bridges and dams, structures which are under huge compressive force but which hold up because they're closely balanced. If you induce a small amount of imbalance, natural forces will complete the job for you.

A dam can be destroyed with one or two torpedoes using contact fuses. The warhead goes off in contact with the dam, and you set it to run pretty deep, so that the water acts as tamping. The damage caused to the dam won't be great, but it begins a cascading failure, caused by the water pressure behind the dam, which will eventually destroy it. (That's why the Germans put torpedo nets in the reservoirs on the Rhine River dams during WWII. For all the good it did them. A British genius named Barnes Wallace figured out how to use something a lot like a big depth charge to do the same thing.)

Bringing a bridge down cleanly, so that you easily can clear away the wreckage, takes dozens or hundreds of cutting charges. But bringing down a bridge in war, when all you need to do is to deny it to an enemy, is really simple. For instance, if it's a suspension bridge, you can do it with just one charge, placed on one of the two suspension cables. (Though they'd probably do them both, just to be sure.) Or you can weaken one bridge support, if it has a long span. Then the weight of the bridge will finish the job through cascading failure.

And a tunnel is also easy to bring down. It doesn't take much damage to unbalance the arch holding the tunnel up, after which the tremendous weight above the tunnel will finish the job.
posted by Steven C. Den Beste at 8:18 PM on January 6, 2008

Steven, yes, we've all seen The Dambusters, and I understand that, but I question the amount of time required to make the tunnel militarily useful again, provided the invaders had the tunnelheads in their control.

If it's days or weeks, perhaps it would make sense, but given air cargo capacities, it is hard to imagine a scenario that would result in MOD concern of the tunnelhead itself.
posted by panamax at 12:18 PM on January 7, 2008

Air cargo is an expensive, time consuming and risky proposition. You can only fit a small amount in even the biggest planes, you have to escort them, you are at risk during takoff, flight and landing. I don't mean to say there wouldn't be risks in using the chunnel, but it's not as easy as that.
posted by furtive at 5:31 AM on January 9, 2008