In time of a war secrecy is absolutely necessary. However, it is only good in moderation. A good example of this is a story of tanks equipped with CDL lighting devices. Their production and testing was so classified that as a result these powerful machines did not come out to the battlefields of World War II.
In 1915 a British officer Oscar De Toren offered an interesting project. Its essence was as follows: a powerful light source is mounted on a car or on a tank to blind the enemy in the dark. When the war ended, the interest in his proposal dissolved, but then De Toren was able to interest the French government in his idea.
The inventor worked as a civilian, that is, sent a proposal on behalf of his syndicate. Interestingly, the project leader was Mitzakis (a British citizen of Greek origin), Technical Advisor - Major-General Fuller, the famous expert in the field of tank weapons. The project was financed by the Duke of Westminster.
The first reveal of the installation took place in 1934 in France, then in 1936, and then the offer once again interested the British Military Office. The demonstration was held in England in 1937 on Salisbury Plain, and, apparently, was quite successful, because after only 10 days after the start of World War II there was an order for the production of 300 units.
The device of de Toren was as simple as it was ingenious. Its goal was to illuminate the darkness of the night battle by a narrow beam of bright, flickering light to blind the observers.
The tower to be mounted on a tank was divided into two sections: the left was for the operator, and the right one housed the CDL unit with the capacity of 13 million candles. The power to supply electricity to two carbon electrodes was produced by its own engine. The intense beam of light first went into a parabolic mirror and then reflected from a flat, polished aluminum plate outside through the gap two inches wide and 24 inches high. It was made so narrow to not allow any enemy bullets in.
The design allows the light to flash at a frequency of six times per second. For self-defense the towers had a machine gun. The angle of the beam emerging from the tower was 19 degrees, allowing the tanks stationed every 30 meters to cover the entire area in front of it at a distance of 180 to 900 meters with beams of light.
Since the CDL program was top secret, a base for re-training the tank crews was placed as far as possible - namely, in Scotland, near Lowther Castle. It was cold, and the living conditions of the personnel were "simply awful", but there could be no fear of German spies and spy planes. The latter was especially important because the new tanks were tested at night, and the light from them was so strong that, for example, one could easily read a newspaper in the neighboring town of Penrith located at a distance of six miles. This light was provided by only 16 tanks.
Therefore, at a threat of an air attack in the Lowther a special warning was issued, and the entire area was immersed in darkness. The life of the farmers in the vicinity of the castle was completely unbearable, because tanks destroyed the fence and crops, but the government paid compensation to all of them.
The first large-scale tests of CDL tanks were held on May 5, 1942, and later it was repeated for the Americans with the participation of American soldiers. They made such a strong impression on General Eisenhower that he immediately ordered to install the same tower on the American tanks. To enable this, another base similar to Lowther was established in South Wales.
After some discussion, the military of the two countries decided that the CDL tanks should be involved against the Germans only massively and in large quantities, which in fact precluded their experimental application in the battle field as their secret could have been revealed. Under these circumstances it was decided to continue the modernization of the tanks and their crews were trained to have them at hand.
At the same time, it gradually became clear that the blinding effect was less than expected. In addition, an unpleasant surprise was the discovery that the green light protection filter on the German 88-mm anti-aircraft gun allowed to clearly see the gap in the tower where the light comes from. The tank crews were disappointed as well, because they were sitting and waiting for orders instead of fighting.
In the meantime, it was decided that since the main armament of the tanks "Matilda" and "Churchill" during the conversion to CDL was removed and the fighting force was considerably reduced, new towers should be put on the American tanks M3 75, which would greatly preserve their combat power, despite the replacement of the tower.
Along with other units, although in the second tier, a division of CDL tanks was deployed in France. However, it was never used for its intended purpose - the night attack of the enemy. They were useless mostly because the military commanders did not know about them due to the veil of secrecy surrounding them.
The Americans used these tanks only on March 1, 1945 to cover the Rhine after the capture of the bridge at Remagen. Then a few weeks later these tanks were used by the English the same way. One tank was hit by the German artillery and several were attacked by aircraft, but with no loss on the British side.
This type of tanks has not been used in the battle any more. The British regarded it as their greatest mistake of World War II. Lt. Gifford Martel, one of the founders of the British armored forces, for example, wrote that a major disaster was a failure to use these tanks in North Africa and Normandy, where the British tanks could have broken through in the area of Caen with their help.
Approximately the same thoughts were expressed by Major-General Fuller, a recognized authority in this area, who argued that it was "the greatest mistake of the war." In 1949, he wrote that the use of CDL tanks could have helped the Allies to occupy the entire Germany, and not to allow Soviet troops there. Marcel Mitzakis received from the Government 20,000 pounds for its development, but it only compensated the costs incurred. He also was very displeased that such an impressive weapon was not used because of the regime of extreme secrecy around it.
The British spent 20 million pounds on this project. 6,000 British and 8,000 American soldiers were trained to use them, but essentially all of these costs were in vain.
In June of 1945, the 43rd Royal Tank Regiment equipped with CDL tanks was sent to India, where in 1946 its tanks, together with the police, were involved in the suppression of riots in Calcutta and acted as police cars with great success. Only one of the tanks of this type survived to our times, and can be seen in the Royal Tank Museum Bovington.