Short intelligence report on German tanks modified for submersion, Tactical and Technical Trends, July 29, 1943. [Editor's Note: The following article is wartime information on enemy equipment published for Allied soldiers. More accurate data on German weapons and equipment is available in postwar publications.]

GERMAN SUBMERSIBLE TANKS The delays and difficulties involved in the transport of tanks across the rivers of Eastern Europe have no doubt forced the Germans to consider very seriously all possible devices for enabling their standard tanks to cross such water obstacles under their own power. a. The PzKw 3 By the summer of 1941, the weight of the PzKw 3 had already been increased by the fitting of additional armor, and it must have been clear that future developments in armor and armament would necessarily involve still further increases in the weight of this tank. While the trend towards increased weight was in many ways disadvantageous, it was definitely helpful in overcoming one of the major difficulties hitherto encountered in adapting standard tanks for submersion, namely the difficulty of obtaining sufficient track adhesion. It is therefore not surprising that the Germans, in the early stages of their campaign in Russia, were actively experimenting with standard PzKw 3's modified for submersion. These experiments met with a certain degree of success, and under-water river crossings are reported to have been made with these modified tanks under service conditions. The measures employed, according to a Russian source, included the sealing of all joints and openings in the tank with india rubber, and the fitting of a flexible air pipe, the free end of which was attached to a float. The supply of air for the crew as well as for the engine was provided for by this flexible pipe. The maximum depth of submersion was 16 feet and the time taken by trained crews to prepare the tanks was about 24 hours. In April 1943, a PzKw 3 Model M examined in North Africa was found to be permanently modified or immersion, if not submersion. There was no mention in the report on this tank of a flexible pipe with float, but this may have been destroyed, since the tank, when examined, had been completely burnt out. The engine air louvres were provided with cover plates having rubber sealing strips around their edges. These cover plates, which were normally held open by strong springs, could be locked in the closed position before submersion. After submersion, the springs could be released by controls from inside the tank. When submerged, air for the carburettor and for the cooling fans was apparently drawn from the fighting compartment. If, therefore, a flexible pipe were used with this tank, no doubt its purpose would be to supply air to the fighting compartment to replace that withdrawn for the carburettor and cooling fans. The two exhaust pipes led to a single silencer mounted high on the tail plate with its outlet at the top. This outlet was fitted a spring-loaded non-return valve, which during normal running could be secured in a fully open position. b. The PzKw 6 More recently still, documents and reports from Russia have shown that the standard PzKw 6 is equipped for submersion to depths of up to 16 feet. In this tank there is provision for hermetically sealing all joints and openings, the doors and covers being provided with suitable rubber seals. The radiators are separated from the engine by a water-tight partition so that, when the tank is submerged, they can take in water from outside the tank, with the cooling fans switched off. Carburettor air in this case is drawn through a flexible pipe, the free end of which is supported by a float, but there appears to be no additional supply of air for the crew. A small bilge pump is also fitted to dispose of any water which may leak into the hull through the various seals, packings and stuffing boxes. It is clear that the PzKw 6 requires only the minimum amount of preparation by the crew before submersion and that its design must have been influenced from the beginning by the requirement that it should be readily submersible. It is quite possible that the PzKw 6 could be submerged to greater depths than 16 feet if it were fitted with a longer air pipe, since, although this tank is little larger than the PzKw 3, it is nearly three times as heavy, and track adhesion is unlikely therefore to be a serious problem.

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