Saturday, August 26, 2006

'The Canal Defence Light'

A modern day photograph of Lowther Castle, Cumbria
[Where the Canal Defence Light was tested during WW2]

While making a comment about a recent posting about Second World War Tanks I referred to the night-time tank manoeuvres that took place on the Lowther Family Estate of the Earl of Lonsdale in the latter part of the war. Lowther Estate is situated a few miles to the south of Penrith, Cumbria. I have since made a few enquiries about the tests. What follows is a brief summary.

In 1942 adapted Matilda tanks arrived at Lowther so that a possible night-time tank strategy might be developed. The turrets of the tanks were adapted to shine intense flickering lights of up to 18 M Candlelight power. It was called locally 'The Candle Defence Light'. (NB -The actual name is 'Canal Defence Light', see the 'Comments' section and contributions by Peter G. for further information about his)

The intended strategy was for tanks to advance in formation and blind the enemy, at least temporarily. As a result, any supporting advance by the infantry would be a cakewalk and much ground would be gained. Among the Generals and VIPs who visited Lowther to see the manoeuvres were Winston Churchill and General Eisenhower, who apparently were suitably impressed.

One defect of the weapon was that the effects of the weapon were mitigated if the enemy wore Ultra-violet glasses. Apparently, it was also felt by some that a weapon that attempted to blind the enemy was 'not quite the done thing'. Also, by the time the weapon was ready for use towards the end of the war, there was less need for a tanks to have this kind of night-time fighting capacity.

Hopefully this makes explanation makes at least some sense to those contributors to the 'Second World War' Blog with a better understanding of tanks. Nowadays, some people in Cumbria refer to these secret tests of tanks using beams of light as using 'laser beams', a term which only came into use in the post-war years.

There is very little information about the night-time tank testing in the Cumbria County Archives. So I can provide few additional details than what has been written here. No doubt there are enthusiasts of tanks who know all about Matilda tanks and can speculate much better about the possible success of this kind of strategy.


Blogger Tomcann said...

The "walzting" Matilia played many roles but this one is new to me although the concept was alleged to be good.Blind the enemy and just walk over the Battlefield and take over.....however
It was late in the evening on Sunday 17th September l944 that the "artificial moonlight" was demonstrated in an actual bsttle.
This took place to the west of Coriano Ridge with the 4th British Div. attacking another ridge between us and Croce, both 46th and 56th Divs had been in action against Croce and Gemmano and were replaced with Maj.Gen.Dudley Wards 4th Div.
I was on top of a four stretcher ambulance jeep heading for Ancona Hospital when all of a sudden the whole area was illuminated by many searchlights hitting the overhead clouds and reflecting back down to the earth... not knowing what was going on we naturally stopped in case it was a ploy by the enemy.
Almost immediately we saw British troops advancing over this field in line order. This didn't last as they were walking towards yet another regiment of the 1st Paratroops who had given us more than trouble all the way from Ortona in the south.
Within minutes they came alive and the Spandau's- Schmeisers and Nebewerfers soon broke up the tidy marching and casualties were mounting fast as they also could see the whole Battlefield.
This was the first time the "artificial moonlight" had been used in Italy and it was obviously the experimental unit.
It was perfected soon afterwards as it was used in the final battles above the Po valley and right to the end on April 29th. '45.

Sunday, 27 August, 2006  
Blogger Peter G said...

This story seems to have grown somewhat. The variant you are referring to is the Matilda II CDL with, later, the Matilda V CDL. The initials CDL stood for Canal Defence Light, not 'Candle Defence Light' - their use initially being envisaged in a Suez defensive role. Essentially the CDL was an armoured housing with a powerful searchlight (nothing secret, just a modified conventional searchlight) mounted in place of the tank's original turret.

The idea was first mooted by a private consortium in the 1930s and it was demonstrated and sold to the War Office in 1937. Its purpose was to illuminate a battlefield in night action, giving a more persistent light than flares could provide. Talk of 'blinding the enemy' is pure fantasy as is its rejection 'because it was not quite the done thing'. Any weapon which could maim or incapacitate soldiers would be grabbed with alacrity; both sides had lethal gas, but neither side resorted to its use in either bombing or on the battlefield for fear of reciprocation; although the Nazis freely used gas secretly on those who could not retaliate. Nor did such considerations as 'not quite the done thing' prevent the use of the atom bombs on Japan. If a country is absolutely sure that it alone possesses a weapon, it will use it. But I digress.

As for the Matilda CDL, in September 1939 an improved armoured searchlight turret was designed and, after trials in 1940, 300 were ordered, enough to equip one brigade in the UK and one in the Middle East (1st Army Tank Brigade) on the Suez Canal, where it remained until 1944. Despite intensive training they were never used in their intended role until 1945 at the Rhine crossing, mainly because suitable opportunities never arose. By 1945, however, the Matildas had been replaced by the Grant as the standard CDL fitted tank.

This came about in early 1943 when M4s had replaced Grants in the 8th Army and it was decided to convert some of the redundant Grants to the CDL role to replace the outdated Matildas. However, the Grants so altered retained their 75mm gun, so keeping an offensive role and had the turret replaced with the armoured searchlight unit which included a ball mounted machine gun in the front face. Later vehicles had a dummy 37mm barrel added to the turret front.

The British brigade was earmarked for operations in NW Europe 1944 but in the event CDL tanks were only used in small numbers to illuminate the night crossings of the Rhine and Elbe in, as I said above, 1945. Other CDL tanks were sent to the Far East in 1945 but never used.

US Armoured Force officers had witnessed CDL demonstrations and 355 US tanks were converted to this role in 1943 to equip six tank battalions for operations in Europe. The American version was designated T10 Shop Tractor to disguise its intended role, but none were used in combat.

As to the use of light in Italy on the Corriano Ridge, dubbed Artificial Moonlight, this had nothing to do with CDL. It was indirect illumination from anti-aircraft searchlights bounced off clouds. This had been perfected during the summer of 1944 and was being used by 1 Canadian Corps. The essence of the idea was to converge the beams of several searchlights over the selected area and the downward glow provided the artificial moonlight.

Sunday, 27 August, 2006  
Blogger Peter G said...

I might have guessed that there would be a web site somewhere. There's more on the Matilda CDL here, including a photo!

Sunday, 27 August, 2006  
Blogger Tomcann said...

Peter -
inasmuch as my brigade of 145thRAC- 12thRTR - 48thRTR comprising the 21st Tank Bde before being re-organised at Cesena on Dec 3 '44 into an Armoured bde, were in fact integral members of 1st Canadian
Corps suporting mainly the 2nd Bde of PPCLI - Seaforths and Loyal Eddies with the odd flurry with 3rd Bde. as the other members of my four stretcher jeep were Seaforths and a Vandoo - Quebec 22e Regt.
It was therefore the modified CDL which we witnessed which was immediately dubbed "Artificial Monnlight' by them wot don't know no better.
I also know that it was close to the Coriano Ridge as this is where one of seven of our Cemetery's is to-day with some 2000 both Canadian and British and strangely - One Russian ?

Sunday, 27 August, 2006  
Blogger Peter G said...


Let me quote directly from the official history: United Kingdom Second Series, Volume VI. Part II, page 290, regarding the breaching of the Gothic Line:

"In this last of 8th Army's battles before it emerged in the plain of Romagna, 4th Division led the way and was the most successful. In its attack across the Ausa on 17th/18th September [1944] [General Sir Alfred Dudley]Ward used the technique of battlefield illumination at night, first introduced into operations by 5th Corps and now adopted by the Canadian C.C.R.A.¹ Anti-aircraft searchlights were deployed a few thousand yards in rear of the front, playing their beams on cloud to provide Artificial Moonlight, while others were deployed on high ground and to the flanks, with the dual purpose of blinding the defence while keeping the assault troops in the lower ground cloaked in darkness. Helped by this illumination 4th Division successfully crossed the Ausa and managed to secure a bridgehead half a mile deep around S. Antimo, two miles short of the ridge road running north-east along the S. Fortunato feature. ... When night came Ward repeated his Artificial Moonlight attack, bridged the Bariolo for tanks and rushed the main ridge around S.Aquilina."

¹The footnote reads "The device had been developed with success by 21st Army Group in Normandy during the previous July"

'Artificial Moonlight' is an official description not a slang field description. On this scale it required the deployment of entire RA Searchlight regiments, not a few CDL Grants. In any event all were in NW Europe at the time.

This is another account of Artificial Moonlight used in Italy in November 1944 by New Zealand forces "In the line north of Faenza, the Division gained full control of the southern stopbank of the Senio early in April. A heavy bombardment by 17 artillery regiments and bombing by heavy and medium bombers and fighter-bombers (all dropping light fragmentation bombs so as not to crater the ground) preceded a night attack on the 9th under “artificial moonlight” created by searchlights." You will find the full text here.

And here a rare shot of Artificial Moonlight in WW2 and from the official Canadian history regarding weapons used in the Italian campaign 'These included the Crocodile flame-throwing tank,the Sherman mounting a 17-pr gun, the Sabot anti-tank ammunition, A.A.
searchlights in the "artificial moonlight" role and the amphibious "Weasel".', here

Sunday, 27 August, 2006  
Blogger ritsonvaljos said...

I think you have explained why I could not find anything sensible about this when I tried Candle Defence Light' on the Search engine. I asked at the County Archives what they had on the manouvres, but we could not find much at all. There could be something there but sometimes depends how an article or file is categorised so that you can find it.

The Tank Museum dealing more specifically about tank developments I would imagine has been able to sort out the legend from the reality. Thanks for the link, Peter, which clarifies a few things. I thought there must be some enthusiasts who would have the correct information to hand.

As stated in the piece I wrote, when you do hear people talking about the testing in Cumbria, they might now refer to 'laser beams' and 'Candle Defence Light'. These are the terms that are passed on by word of mouth, that's if they know anything at all. So I can see how the inaccuracies have arisen. It is better that they are not propogated further. Now I have a little bit better idea of what it was all about. There are still a lot of things I've found that happened in WW2 where the actual facts are not widely known. For example, there were a lot of Air Force plane crashes but it is difficult to find them documented to any detail.

Possibly, the CDL and 'Artificial Moonlight' would have worked better earlier in the war, during the North African campaign? Do you think they would have been better using the techniques defensively rather than offensively?

Thanks for the clarification and the additional information.

Sunday, 27 August, 2006  
Blogger Tomcann said...

As always from Peter - the erudite explantion of the things that we experienced without knowing what it was all about.
One point Joseph - it's doubtful if this system had any relevancee in the desert as clouds were few and far between !

Sunday, 27 August, 2006  
Blogger Tomcann said...

Peter - on a closer look at the cdn Official History of Lt Col Nicholson - I find the words of Lt.Gen Burns in his report to the Chief of staff at CMHQ ' September 2nd - "The Gothic line was completely broken"
We had been hammering away at this from 30th August to Sept 1 at the River Foglia at Montelabbate and thence to Pozzo Alto and Monteluro.
The Cdn 5th Armoured then passed through and subdued Tomba di Pesaro - now called something else Tuvalu - with the BC Dragoons who lost their Colonel the brother of the Corp Commander and claimed all the credit.
The 5th Corps of 46 and 56th Divs went forward to the horrific battles at Croce and Gemmano on our left flank, then the 4th Div passed through on our left as we were hammering away at San Martino (15th-19th septemeber)on the Coriano Ridge. The Ausa was crossed by 4th Div to the left of San Fortunato(18-19th sept) at the River Budriolo between San Antimo and Sant'Aquilanna. The 1st Brit armoured was on their left flank.
By that date we were hammering a way at San Fortunato on 4th Div's right flank.
So the Gothic line - proper - was breached on the night of 1/2nd September - the battles on Coriano Ridge of Croce - Gemmano - San Martino and San Fortunato were something else!!! In comparison the 'breaching' was a walk in the park.

Monday, 28 August, 2006  
Blogger Peter G said...

Just to tie up some loose ends on illuminating a battlefield, since I can find nothing useful on this topic on the Web.

Ideally you would just drive up your searchlights to the front, switch them on, and hey presto you have a lit battlefield and in addition you dazzle the enemy. Then there is a short volley of of light-arm fire and your lights are shot out, so not a good idea. This is the problem that had to be solved.

Initially light was used defensively in WW1 with flares being sent up at irregular intervals throughout the night to light up no-mans land and hopefully detect raids or wiring parties. But flares, though very good, do not last long and are less effective in strong wind.

Artificial Moonlight in WW2 sought to solve the problem by setting searchlights back out of range then shining them at a set angle (depending on cloud density and height) to obtain diffused bounced lighting over a wide area.

In 1939/42 the main problem was the defence of the Suez Canal an area where clouds are rare. Any searchlight used in in a battle defensive role with direct lighting wouldn't last two minutes. Hence the need for an armoured source of light and the birth of CDL, using existing apparatus.

The General Electric 1942 searchlight was a five foot diameter lamp producing 800 million candela, powered by a 15 KW generator, giving an effective beam visibility of up to 35 miles. Earlier models were less efficient but still as bulky. The problem was to get this technology into an armoured turret and shine it through two narrow vertical slits providing adequate cooling. This was solved and put into production and troops trained. But as the danger to the Suez Canal first receded then vanished the use for CDL tanks dwindled too. It was only at broad river crossings that they came into their own, hence their valuable contribution to both the Rhine and Elbe crossings.

There is much use of the word 'blind' and 'blinding the enemy' even in official accounts and this wording may have contributed to the current myth of a secret weapon; but 'blind' is used in the sense of 'dazzle' - the sun will blind you if you stare at it long enough but no one in their right senses would do so. We often inadvertently catch direct sight of the sun and are dazzled. CDL would only be useful as a weapon for the first time if the intention had been to blind an enemy; after that even cheap goggles based on welder's goggles would suffice to nullify it - in an emergency use your hand to give shade. It was used to light up a river crossing, not to permanently incapacitate the enemy.

Now let me speculate (speculate? My university tutors would have a fit! lol). Training would have to be done in a remote area because of blackout restrictions, a remote part of Cumbria sounds ideal. Then there is no way that you can stop the locals seeing entire fields lit up night after night. As Frank rightly observes, propaganda takes over. A few tales are spread in the pub about a secret weapon which is going to blind the enemy. You also suggest that people stear clear because it is highly dangerous to watch, emphasising that "It's all very hush hush old chap"; Such a warning would guarantee it spreading.

Monday, 28 August, 2006  
Blogger Peter G said...


That's a useful account you gave of the breaking of the Gothic Line and preliminary battles. The British Official History goes into far more detail (useful, but at times making it difficult to see the whole picture), for example Volume VI - Part II is a separate book of 532 pages with 28 maps, yet this hefty volume just covers events from June to October 1944.

Your knowledge of these events is second to none, Tom. But since you are interested in the Canadian contribution and are reading the Canadian Official History, let me quote a tribute to them in the British Official history:

"1st and 2nd September were proud days for the 1st Canadian Corps. In spite of fatigue in the dust laden atmosphere and stifling heat which enveloped the battlefield in the first days of September, morale was unquestionably high as every man sensed that he was writing an important page in Canadian history. The Canadian Official historian quotes an apt description:
In places the dust lies like powdered snow to a depth of 3 to 4 inches. It is impossible to see a moving tank. You are only aware of its presence by the turbulent cloud of dust which accompanies it ...
The remarkable thing is that in all this filth, fatigue and bodily discomfort, the same old time-worn humour and perpetual good nature persists.

Hard times and good men!

Monday, 28 August, 2006  
Blogger Tomcann said...

Peter - that's a fair tribute to the men at that time as to-day is the anniversary of us approaching the Foglia with it's anti tank ditch which seemed to go for miles - the minefields - plus the river - which happily was fairly well dried up - and the fact that we knew that both 1st Paras and 26th Panzers were on their way to hold us - so had to rush to push the 71st Inf to one side, and get through to Pozzo Alto - and allow the 5th Cdn to pass and hit Tuvallu.
I had a big arguement about that battle many years ago with a Lt Col of the B.C. Dragoons in Kelowna who were forever boasting that they broke the Gothic Line at Tuvallu.
I finally shut him up by recalling that he - personally - as the Squadron leader of B squdn, had been detailed to wait for The Perth Regt to catch up before hitting Tuvalu - the Perths were held up and so the brother of the Corps Commander - Tommy Burns - as Lt Col of the Dragoons decided to carry on with a wild ride - head on into that town. He got away with it but was fatally wounded in the process.
When we heard of this - we in the 21st TB superiorally - put it down to inexperience of Tank Warfare !They lost a whole squadron of Sherman's.
Hopefully this anniversary should be much more peaceful as
"er indoors" is now outdoors in the U.K. and so Bella and I can leave the dishes in the washing m/c for a few days until we run out.

Monday, 28 August, 2006  
Anonymous Richard Jones said...

Have just been reading these notes about the CDL with interest. My father was involved with them and I have a diary of what seems to be all his locations during the was including "Lowther Castle" wher CDL training took place. I have however has difficulty in matching his dates with ant sort of action with CDL!
Kind regards
Richard Jones

Thursday, 14 May, 2015  

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