What effect would a cross channel tunnel have on WW2?

[wuzak]

From the early 19th century there were proposals to build a cross channel tunnel from England to France.

In the 1880s a tunnel was actually started, with excavation from both the French and English sides, but this was abandoned due to the British military fearing it would aid a cross channel invasion.

After WW1, in the interwar period, there were a few proposals for a cross channel tunnel, one of the proponents of the tunnel being Winston Churchill.

After France fell there were fears in Britain that the Germans could build a tunnel, or two, in 18 months.

My question is - if the tunnel from the 1880s was completed, or one of the proposals from the 1920s was built, how would that effect the war?

Would it increase the chances of a successful invasion of Britain by Germany?

Or would such a tunnel be too easily defendable?

 

[Thumpalumpacus]

I'd plant mines alongside it, solid-wired on my end. Blow the front-side, clog it up, and do aerial ground attack as the invading force has to back up.

 

[Alan Stevens]

From the early 19th century there were proposals to build a cross channel tunnel from England to France.

In the 1880s a tunnel was actually started, with excavation from both the French and English sides, but this was abandoned due to the British military fearing it would aid a cross channel invasion.

After WW1, in the interwar period, there were a few proposals for a cross channel tunnel, one of the proponents of the tunnel being Winston Churchill.

After France fell there were fears in Britain that the Germans could build a tunnel, or two, in 18 months.

My question is - if the tunnel from the 1880s was completed, or one of the proposals from the 1920s was built, how would that effect the war?

Would it increase the chances of a successful invasion of Britain by Germany?

Or would such a tunnel be too easily defendable?

I would argue that the civil engineering technology was not yet at a level to build a 32 mile long tunnel under the English Channel.

 

[mjfur]

There would have been a Starbucks on the French side of the tunnel to serve hot coffee to the GI's. With the GI's full of caffeine the war would have ended six-nine months sooner.

 

[EwenS]

I would argue that the civil engineering technology was not yet at a level to build a 32 mile long tunnel under the English Channel.

Agreed. Certainly not in the 18 month timescale claimed.

After 20 years of site investigation and planning a route across construction work started in 1988. Working from both ends from 1988 with late 20th century automated tunnel boring machines both cutting the tunnel and lining it with pre-cast concrete panels it took until 1 Dec 1990 to achieve a breakthrough in the first (narrower service tunnel). The route chosen was not simple to achieve due to the geology.

Channel Tunnel - Wikipedia

en.m.wikipedia.org

I'm sure the British Army would have welcomed narrow columns of emerging German troops with the open gates of a POW cage. Plenty of time to plan for that.

Edit:- Just for comparison it took the Japanese 6 years 1936-42 to construct the twin tunnels of the Kanmon Rail Tunnel between Kyushu & Honshu islands. Don't know about the geology, but they were only 3.6km long.

Edit 2. Each end of the 1880 tunnel had only progressed about a mile in 9 months before the project was abandoned. Slave labour doesn't really help much due to the narrow working face at the front of the tunnel.

 

[Alan Stevens]

Agreed. Certainly not in the 18 month timescale claimed.

After 20 years of site investigation and planning a route across construction work started in 1988. Working from both ends from 1988 with late 20th century automated tunnel boring machines both cutting the tunnel and lining it with pre-cast concrete panels it took until 1 Dec 1990 to achieve a breakthrough in the first (narrower service tunnel). The route chosen was not simple to achieve due to the geology.

Channel Tunnel - Wikipedia

en.m.wikipedia.org

I'm sure the British Army would have welcomed narrow columns of emerging German troops with the open gates of a POW cage. Plenty of time to plan for that.

Edit:- Just for comparison it took the Japanese 6 years 1936-42 to construct the twin tunnels of the Kanmon Rail Tunnel between Kyushu & Honshu islands. Don't know about the geology, but they were only 3.6km long.

Edit 2. Each end of the 1880 tunnel had only progressed about a mile in 9 months before the project was abandoned. Slave labour doesn't really help much due to the narrow working face at the front of the tunnel.

The Simplon Tunnel in the Alps opened in 1906 and is 12.5 miles long. There were other long mountain tunnels, but for underwater tunnels the lengths were two miles and under, such as the Holland Tunnel and the Lincoln Tunnel.

32 miles under a sea strait is far beyond what anyone managed to build pre-WW II. Ventilation is also a major engineering issue.

 

[ThomasP]

FWIW

There is/was the Rothschönberger Stolln dewatering adit, part of the "Revierwasserlaufanstalt Freiberg - Wikipedia", mostly built between 1844 and 1877, at a little over 31 miles long by 10-20 ft wide. It was the longest tunnel in the world until the Delaware Aqueduct, built between 1939 and 1945 to feed water to New York city and metro area, at a little over 85 miles long with a diameter of 13.5 ft.

 

[GTX]

There would have been a Starbucks on the French side of the tunnel to serve hot coffee to the GI's. With the GI's full of caffeine the war would have ended six-nine months sooner.

And if you had Australians in the mix it would have ended even quicker due to their going elsewhere to look for decent coffee…

 

[Alan Stevens]

FWIW

There is/was the Rothschönberger Stolln dewatering adit, part of the "Revierwasserlaufanstalt Freiberg - Wikipedia", mostly built between 1844 and 1877, at a little over 31 miles long by 10-20 ft wide. It was the longest tunnel in the world until the Delaware Aqueduct, built between 1939 and 1945 to feed water to New York city and metro area, at a little over 85 miles long with a diameter of 13.5 ft.

But they were not large enough to carry trains or vehicles.

The Thames Tunnel, built under the River Thames in London, was the first underwater tunnel in the world and was 1,300 ft (400 m) long, opened in 1825.

The Holland Tunnel, built under the Hudson River in 1927, was the first mechanically ventilated underwater vehicular tunnel.

The first underwater tunnel that was at least five miles long is the Seikan Tunnel in Japan. Completed in 1988, it connects the islands of Honshu and Hokkaido and is the world's longest undersea rail tunnel, with a total length of 33.46 miles (53.85 kilometers). The undersea portion is 23.3 kilometres (14.5 mi).

I would say that the 1980s therefore is a good benchmark for when the technology and funding for the English Channel Tunnel was first feasible.

 

[GrauGeist]

To be honest, I don't think that a Commander would risk his army in such a precarious situation.

All the British would have to do, is wait until the invaders reached the English side and detonate the mines, resulting in a total annihilation of countless troops.

Much like in the Biblical story of Moses releasing the part in the Red Sea upon safely reaching the east side, which engulfed Pharoh's charioteers and troops who were in hot pursuit.

 

[Snautzer01]

To be honest, I don't think that a Commander would risk his army in such a precarious situation.

All the British would have to do, is wait until the invaders reached the English side and detonate the mines, resulting in a total annihilation of countless troops.

Much like in the Biblical story of Moses releasing the part in the Red Sea upon safely reaching the east side, which engulfed Pharoh's charioteers and troops who were in hot pursuit.

On the other hand it was common knowledge that the Maginot line was unbreakable and Troy wouldnt fall and that strange RN ship against the the heavily dry dock at St Nazaire would not be a problem.
I see what you are getting at but well...

 

[ThomasP]

To be fair, the under-channel tunnel idea would only work if it could be built in secret - which secret would be impossible to keep due to the time involved, if for no other reason.

 

[swampyankee]

One may wonder what the greater interest in maintaining contact with the Europe, shown by the amount of treasure and co-operation with France needed to build a cross-Channel tunnel, would indicate regarding the UK's government and its interest in, say, more actively supporting France against the increasingly militaristic Germany.

 

[Alan Stevens]

To be fair, the under-channel tunnel idea would only work if it could be built in secret - which secret would be impossible to keep due to the time involved, if for no other reason.

The solution to any tunnel being denied enemy access, is not to blow up the whole tunnel. That would be wasteful because they would eventually have to rebuild the tunnel.

Just blow up several hundred feet of tunnel at the portal. If the enemy tries to retake them they can be bombed with Tallboys.

 

[eljefe]

I would think that capturing the enemy end intact would be the ultimate commando operation. You wouldn't even think about marching your own troops through unless both ends were secure, and the middle likely safe from any naval operation.

 

[wuzak]

I would think that capturing the enemy end intact would be the ultimate commando operation. You wouldn't even think about marching your own troops through unless both ends were secure, and the middle likely safe from any naval operation.

So a tunnel would have been great for evacuating after the fall of France, so long as you can hold the tunnel entrance and you can get your troops to the tunnel.

 

[GrauGeist]

So a tunnel would have been great for evacuating after the fall of France, so long as you can hold the tunnel entrance and you can get your troops to the tunnel.

Considering the Wehrmacht's fateful pause while the BEF and French were crowded unmolested on the beach, I'd suspect their escape via the tunnel would have been successful.

 

[Airframes]

No, old boy.
At the first sign of a bit of bother, we old Brits would have set up very decent barriers, with the odd Policeman demanding to inspect Passports, inspect luggage and confiscate any illegal import of French cheese and wine, as well as banning French (and especially German) cars from continuing before they'd paid the current Road Tax - but only after tea and crumpets, don't you know !