Chapter 427 Preparations for Landing (2)

After the defeat at Dieppe, the Allies quickly realized they had made a significant mistake in the timing of their tank landings: to allow tanks and infantry to attack the beachhead simultaneously, the Allied tank landing ships had to approach the beach as closely as possible before releasing the vehicles. However, a ship with a displacement of 200 tons and carrying 9 tanks inside would undoubtedly become an easy target for enemy fire.

At such close range, even light artillery could easily inflict heavy damage on the landing ships. Once a ship was damaged, it meant that all the tanks inside could not be deployed in time for combat, resulting in a significant loss of combat power. This problem could be solved by placing tanks individually on smaller landing craft, but the Allies did not have enough landing craft available. The best solution was for the landing ships to release the tanks while maintaining a distance from the beachhead, allowing them to swim ashore on their own.

However, the defense capabilities of light amphibious tanks were too weak to withstand anti-tank gun attacks, and the better-protected medium tanks were too heavy—such as the various models of American-made Sherman tanks equipped by the British army at the time, each weighing about 30 tons, and the domestically produced Churchill tanks even heavier at 38 tons, which would sink like a weight once in water.

Therefore, Hobart turned his attention to the "duplex drive" equipment (abbreviated as DD) developed by inventor Nicholas Straussler.

Straussler (1891-1966), born in Hungary, had designed various types of foldable bridging equipment before obtaining British citizenship in 1933. The purpose of the DD device was to provide amphibious capability to large vehicles, including tanks. Its main structure was a foldable canvas waterproof curtain tightly installed around the upper body of the tank. When the waterproof curtain was raised, it provided buoyancy and sealed waterproofing for the tank, preventing it from sinking or taking on water even when submerged. In addition, the DD device included a propeller propulsion system directly driven by the tank's engine, allowing the tank to move at a steady speed in the water.

In June 1941, the British army tested a Valentine airborne tank equipped with the DD device at Brent Reservoir, and the results were a great success. The DD device was finalized in June 1942. Initially, the British army chose the Valentine infantry tank, with a combat weight of 18 tons, as the main carrier for the DD device, and a total of 650 Valentine Mk III (equipped with a 2-pound gun) and Mk VIII (equipped with a 6-pound gun) were converted into Valentine DD tanks. However, Hobart considered these old tanks outdated and decided to use the newer American-made Sherman series tanks as the new carriers for the DD device.

The first Sherman tank was converted in 1943, equipped with a foldable canvas cover lined with a circular rubber air hose frame, installed on a boat-shaped platform welded around the tank's body. The operation involved inflating the rubber frame through an air tube, raising the canvas to a high point above the turret as the gas filled the rubber frame, with the support locking the canvas in place. The operation was completed by the tank crew on the deck of the tank landing ship in just 15 minutes. Once the canvas was deployed, the tank could be launched into the water. The deployed canvas provided nearly 1 meter of freeboard space, and the entire vehicle was powered by two small propellers installed at the rear of the body, with direction controlled by swinging the propellers and additional steering achieved by a small rudder controlled by the tank commander installed outside the turret.

The tank's speed on water was slow, depending on sea conditions. Sea conditions above level 5 meant a higher risk, but this limitation was often disregarded, leading to disastrous accidents. When the water depth reached 1.5 meters, the canvas could be retracted, and then it was time for the "DD Sherman" tank to shine, as its main gun could fire.

The "DD Sherman" tank did not have a navigational machine gun, but its cannon provided strong and direct fire support for the British soldiers during the landing operations, especially evident in the Normandy landing campaign on June 22, 1944. Once out of the water, the propellers at the rear of the body could be retracted, and off the beach, it was a standard main battle tank.

Germany also researched amphibious tanks during World War II, and the Panzer II had an amphibious version. However, such light tanks with weak protection and firepower did not meet their requirements; they wanted to send their main battle tanks.

It is unknown which talent in the German army, after seeing the navy's submarines, had a wild idea to let tanks swim across the English Channel. Honestly, this idea was as unbelievable as someone telling you that the sun would rise from the south tomorrow. Yet, the German army's high command and the little mustache, perhaps dizzy from the war situation, actually approved this plan. And the German engineers, not only did as the military requested, but they also succeeded.

They planned to modify the Panzer III or Panzer IV to operate underwater. In the end, the German engineers chose the Panzer IV because it was the largest, most powerful, and best-protected tank in Germany at the time. They selected the Panzer IV Ausf. D and E models as the basis for development, simply because they were the most produced models.

The modification of the Panzer IV involved sealing the main gun and adding a protective cover, sealing other potential leak points such as machine gun ports and observation windows with waterproof materials. The hatches, turret, and armored parts of the vehicle were fitted with rubber seals and drain covers. In appearance, compared to the standard Panzer IV, the difference was not significant, except for the additional fixed ventilation pipes and support frames for the pipes.

However, unlike the original Panzer IV, it had an additional ventilation pipe and an underwater navigation compass. The ventilation pipe was equipped with a sealed cap, and the exhaust pipe had a one-way exhaust device. When the tank was submerged, air was drawn into the cabin through the ventilation pipe. The ventilation equipment consisted of an 18-meter-long ventilation hose and its front-end buoy. The buoy of the ventilation equipment was fitted with an air intake and a radio antenna, and the air entering the tank's cabin came from the buoy. As the submerged tank moved underwater, its buoy floated on the surface, supplying air to the cabin through the buoy's mouth.

After extensive modifications, this type of submerged tank could reach a maximum depth of 15-18 meters underwater and could also move along the seabed. It seemed that such tanks were now combat-ready, and if several armored groups were assembled, these submerged tanks could attack Britain.

But reality was far from ideal.

Firstly, the unfortunate ventilation pipe relied entirely on the buoy on the surface. If the buoy took on water, then water would flow into the tank through the ventilation pipe, potentially drowning the people inside. Secondly, this type of tank could only move underwater for a maximum of thirty minutes. Beyond that, the concentration of carbon monoxide inside the tank would become too high, posing a risk of poisoning the crew members. If the concentration exceeded the specified limit, there was a danger of explosion.

Moreover, although the theoretical diving depth of this submerged tank was eighteen meters, that was only possible when the water surface was calm. If the waves were too large, the tank was likely to be overturned by the water flow. When in use, the submerged tank had to be transported by a barge to the nearshore waters and then launched not far from the target coast. The water surface had to be a gentle sandy area; otherwise, the tank would anchor directly. In addition, its visibility in the water was very limited, and if it encountered obstacles, it would probably be difficult to navigate around them. If it could not bypass the obstacles or anchored, then it would stop in place and ultimately become a true submerged tank, the kind that never resurfaces.

Even if it did make it ashore, it could not immediately open fire. Due to the need for the tank to undergo deep submersion, the Germans used a large amount of sealing material for waterproofing during construction, resulting in the tank's weapons being unusable immediately after landing. Important components such as the cannon, machine guns, and sighting devices were filled with a large amount of sealing rubber and foam materials.

The tank's ventilation pipe also had to be removed, as these 18-meter-long hoses greatly hindered the tank's normal progress, and the rear exhaust pipe also needed to be reinstalled. Therefore, the crew had to remove these diving devices before the tank could exert its true combat power. By the time all this was done, the enemy might have already launched a counter-charge. Thus, this weapon was not very practical. It could be said to be somewhat sensationalist.