Canal Defence Light
Encyclopedia
Canal Defence Light was a British "secret weapon" of the Second World War.
It was based upon the use of a powerful carbon-arc
searchlight
mounted on a tank. It was intended to be used during night-time attacks, when the light would allow enemy positions to be targeted. A secondary use of the light would be to dazzle and disorient enemy troops, making it harder for them to return fire accurately. The inaccurate name Canal Defence Light was used to conceal the device's true purpose.
was used, replacing its normal turret with a cylindrical one containing both a searchlight and a machine gun. This was later replaced by the US M3 Grant
which was superior in several ways. It was a larger, roomier tank, yet was also faster and so better able to keep up with tanks such as the Sherman. It was armed with a hull–mounted gun, which was unaffected by the replacement of its normal turret with the searchlight turret.
The searchlight turret included a station for an operator. The light emerged from a vertical slit that was just 2 inches (5.1 cm) by 24 inches (61 cm), its comparative smallness reduced the chance of damage to the optical system by the entry of bullets. The beam diverged at 19° horizontally and 1.9° vertically, forming a pool of light around 34 by 340 yd (31.1 by 310.9 m) at a range of 1000 yards (914.4 m). The turret could rotate 360° and the light beam elevated or depressed by 10° from the horizontal.
Blue and amber filters allowed the light to be coloured as well as white. A shutter could flash the beam on and off up to twice a second.
It was found the blue light caused the CDL tank to appear to be at a greater distance, and blue and amber light beams from two CDL tanks could combine to illuminate a target with white. A flashing beam would further dazzle and disorient enemy troops by not giving their eyes a chance to adapt to either light or darkness.
The project was shrouded in secrecy. It was tested during Exercise Primrose in 1943 at Tighnabruaich
, Scotland with the result that it was determined to be "too uncertain to be depended upon as the main feature of an invasion".
near Penrith
, and were based at Brougham Hall
, Cumberland, spent 1942 and 1943 in the Middle East without seeing action, and returned to the UK in April 1944. They landed in Normandy on 12 August 1944, and saw no action until 29 September 1944 when they were ordered to transfer all their equipment to the 42nd and 49th
Royal Tank Regiments, and were retrained to operate the American amphibious LVT-4
, known by the British Army as the Buffalo Mark IV.
In their turn, the 42nd and 49th Royal Tank Regiments were largely inactive for the remainder of the war, when all three units were disbanded after the end of hostilities.
in March 1945. The Germans attempted to attack the bridges at night using swimmers and floating mines, dropped into the river upstream. The armour of the CDL's made them more suitable for this task than conventional searchlights as, in some sectors, the East bank of the river was held by German forces who subjected the CDL tanks to considerable artillery and small-arms fire. Curiously, the actual use of the system resembled its name, which was intended to be spurious.
Later, the battle moved East and the CDLs were used to illuminate the bridges for the benefit of engineers carrying out maintenance. Conventional searchlights were more suited for this but none were available. The CDLs were eventually replaced by captured German searchlights.
still exists as part of the collection of the Royal Armoured Corps Tank Museum
at Bovington, Dorset, in Britain. It is the only one of its type known to exist. There are no Grant examples.
It was based upon the use of a powerful carbon-arc
Arc lamp
"Arc lamp" or "arc light" is the general term for a class of lamps that produce light by an electric arc . The lamp consists of two electrodes, first made from carbon but typically made today of tungsten, which are separated by a gas...
searchlight
Searchlight
A searchlight is an apparatus that combines a bright light source with some form of curved reflector or other optics to project a powerful beam of light of approximately parallel rays in a particular direction, usually constructed so that it can be swiveled about.-Military use:The Royal Navy used...
mounted on a tank. It was intended to be used during night-time attacks, when the light would allow enemy positions to be targeted. A secondary use of the light would be to dazzle and disorient enemy troops, making it harder for them to return fire accurately. The inaccurate name Canal Defence Light was used to conceal the device's true purpose.
Description
The searchlight was mounted in an armoured turret fitted to a tank. Initially the Matilda tankMatilda tank
The Infantry Tank Mark II known as the Matilda II was a British infantry tank of the Second World War. It was also identified from its General Staff Specification A12....
was used, replacing its normal turret with a cylindrical one containing both a searchlight and a machine gun. This was later replaced by the US M3 Grant
M3 Lee
The Medium Tank M3 was an American tank used during World War II. In Britain the tank was called "General Lee", named after Confederate General Robert E. Lee, and the modified version built with a new turret was called the "General Grant", named after U.S. General Ulysses S. Grant.Design commenced...
which was superior in several ways. It was a larger, roomier tank, yet was also faster and so better able to keep up with tanks such as the Sherman. It was armed with a hull–mounted gun, which was unaffected by the replacement of its normal turret with the searchlight turret.
The searchlight turret included a station for an operator. The light emerged from a vertical slit that was just 2 inches (5.1 cm) by 24 inches (61 cm), its comparative smallness reduced the chance of damage to the optical system by the entry of bullets. The beam diverged at 19° horizontally and 1.9° vertically, forming a pool of light around 34 by 340 yd (31.1 by 310.9 m) at a range of 1000 yards (914.4 m). The turret could rotate 360° and the light beam elevated or depressed by 10° from the horizontal.
Blue and amber filters allowed the light to be coloured as well as white. A shutter could flash the beam on and off up to twice a second.
It was found the blue light caused the CDL tank to appear to be at a greater distance, and blue and amber light beams from two CDL tanks could combine to illuminate a target with white. A flashing beam would further dazzle and disorient enemy troops by not giving their eyes a chance to adapt to either light or darkness.
The project was shrouded in secrecy. It was tested during Exercise Primrose in 1943 at Tighnabruaich
Tighnabruaich
Tighnabruaich is a village on the Kyles of Bute in Argyll and Bute, Scotland.Tighnabruaich is part of Argyll's Secret Coast, just an hour and a half west of Glasgow, and is nestled along the east coast of Loch Fyne and stretching into the beautiful Kyles of Bute.Tighnabruaich is popular for...
, Scotland with the result that it was determined to be "too uncertain to be depended upon as the main feature of an invasion".
Units that were equipped with CDL
The 11th Royal Tank Regiment was raised in January 1941 and designated for the CDL role in May 1941. The unit trained at Lowther CastleLowther Castle
Lowther Castle is a country house in the historic county of Westmorland, which now forms part of the modern county of Cumbria, England. It has belonged to the Lowther family, latterly the Earls of Lonsdale, since the Middle Ages.- History :...
near Penrith
Penrith, Cumbria
Penrith was an urban district between 1894 and 1974, when it was merged into Eden District.The authority's area was coterminous with the civil parish of Penrith although when the council was abolished Penrith became an unparished area....
, and were based at Brougham Hall
Brougham Hall
Brougham Hall is located in the village of Brougham just outside Penrith, Cumbria, England. The oldest part of the hall is the Tudor building, which dates back to around 1500 and was once the scene of a bloody battle between the English and Scots....
, Cumberland, spent 1942 and 1943 in the Middle East without seeing action, and returned to the UK in April 1944. They landed in Normandy on 12 August 1944, and saw no action until 29 September 1944 when they were ordered to transfer all their equipment to the 42nd and 49th
49th Royal Tank Regiment
The 49th Royal Tank Regiment was an armoured regiment of the British Army during the Second World War. It was part of the Royal Tank Regiment, itself part of the Royal Armoured Corps....
Royal Tank Regiments, and were retrained to operate the American amphibious LVT-4
Landing Vehicle Tracked
The Landing Vehicle Tracked was a class of amphibious vehicles introduced by the United States Navy, Marine Corps and Army during World War II. Originally intended solely as cargo carriers for ship to shore operations, they rapidly evolved into assault troop and fire support vehicles as well...
, known by the British Army as the Buffalo Mark IV.
In their turn, the 42nd and 49th Royal Tank Regiments were largely inactive for the remainder of the war, when all three units were disbanded after the end of hostilities.
Deployment and Combat
The system was highly secret as surprise was considered essential to its use. This hampered its employment as commanders were often unfamiliar with it and did not consider it when drawing up plans for attack. CDLs were never used for their intended purpose; however, they saw use by US forces in protecting bridges after the crossing of the RhineOperation Plunder
Commencing on the night of 23 March 1945 during World War II, Operation Plunder was the crossing of the River Rhine at Rees, Wesel, and south of the Lippe River by the British 2nd Army, under Lieutenant-General Sir Miles Dempsey , and the U.S. Ninth Army , under Lieutenant General William Simpson...
in March 1945. The Germans attempted to attack the bridges at night using swimmers and floating mines, dropped into the river upstream. The armour of the CDL's made them more suitable for this task than conventional searchlights as, in some sectors, the East bank of the river was held by German forces who subjected the CDL tanks to considerable artillery and small-arms fire. Curiously, the actual use of the system resembled its name, which was intended to be spurious.
Later, the battle moved East and the CDLs were used to illuminate the bridges for the benefit of engineers carrying out maintenance. Conventional searchlights were more suited for this but none were available. The CDLs were eventually replaced by captured German searchlights.
Surviving example
A CDL equipped Matilda tankMatilda tank
The Infantry Tank Mark II known as the Matilda II was a British infantry tank of the Second World War. It was also identified from its General Staff Specification A12....
still exists as part of the collection of the Royal Armoured Corps Tank Museum
Bovington Tank Museum
The Tank Museum is a collection of armoured fighting vehicles in the United Kingdom that traces the history of the tank. With almost 300 vehicles on exhibition from 26 countries it is the second-largest collection of tanks and armoured fighting vehicles in the world.The Musée des Blindés in France...
at Bovington, Dorset, in Britain. It is the only one of its type known to exist. There are no Grant examples.
External links
- Report on DDay preparations
- Now It Can Be Told! - Tanks That Turn Night Into Local Day, The War IllustratedThe War IllustratedThe War Illustrated was a British war magazine published in London by William Berry . It was first released on 22 August 1914, eighteen days after the United Kingdom declared war on Germany, and regular issues continued throughout World War I...
, November 23, 1945.