Originally Posted by MarkV
Allocating the name Canal Defence Light to the type of tank shown was a double deception as it both confused the picture around the real Canal Defence Lights and concealed the real purpose behind these vehicles. This was to facilitate mass night time attacks by Allied armor by illuminating the battlefield to order. AFAIK the original operation for which they were intended failed to materialise but they were deployed in a number of others to provide "artificial moonlight" by projecting their search light onto the base of clouds to reflect downwards and provide the equivalent of very bright moonlight over a specified area of the battlefield.
But the CDL tanks were
able to dazzle the enemy due to the shutter to which Fletcher refers in the video, and this was an important consideration secondary to providing light on the battlefield.
Hunnicutt: "The shutter was operated either manually or automatically at two rates of speed by an electric motor producing a dazzling flicker. Colored filters also could be inserted into the 13,000,000 candlepower beam. When combined with the blinding effect of the flickering light they were intended to confuse the enemy during a night assault."
Zaloga: "The engineers came up with other innovations, such as the use of a shutter to enable the beams to flicker on and off to confuse enemy gunners. Colored filters were also developed to make it more difficult for the enemy to determine the range to the lights."
Macksey: "However, the C.D.L. was also capable of blinding the enemy with a flicker induced by the automatic movement of a shutter across the light aperture, and this facility, it was claimed, raised the weapon system above a mere battlefield aid by transforming it, in the minds of its keenest advocates, into a battle-winning weapon in its own right."
Originally Posted by MonsterZero
I've seen this vehicle. The question is why? Self propelled artillery fires a few shots and drives away to change position in case of counter-battery fire. Why abandon the men to their own fate and drive away in a useless vehicle without armament? The position may become too dangerous for the vehicle to return, forcing the turret crew will escape on foot. When they escape on foot, generally they are picked off by enemy musketry.
This vehicle was not a tank: the concept was being developed as a self-propelled howitzer. Instead of turning the entire vehicle as on many other designs of the time, the Germans wanted one that could traverse on the vehicle. Regarding the dismountable howitzer, Spielberger: "Since the armored artillery, and therefore the self-propelled artillery, were indispensable in defensive actions, and on the other hand the valuable vehicles should not be exposed to enemy fire and weather, dismounting the gun became a requirement. The value of the self-propelled mount was its high degree of mobility, which required constant maintenance. In a firing position this was only possible within certain limits. In addition, a dismounted gun provided a considerably smaller target in defensive action."
It can be thought of as similar to the gun carriers from World War I, which were made to either have their ordnance fired from the carrier or to transport the weapon to a firing position and dismount it. When dismounted, the howitzer in this German concept was armored against artillery fragments and small arms, which was something its towed brethren couldn't claim.