DD tank

Valentine DD tank with screen lowered

Valentine DD tank with screen lowered

The DD tank (Engl. duplex drive tank “tank with two drive types “) was developed during the Second World War for amphibious operations swimming tank type.  The term is mainly related to the converted, inter alia, in Operation Overlord used moderate U.S. M4 Sherman used.

The swimming tank was to support the infantry actions required at the landing beaches.  Equipped with the ability to swim, the tanks were of landing craft are launched and reach the beach under their own power.  Thus did the Allies gain an advantage, as the German defenders were not prepared for tank attacks from the sea-side.  On Juno Beach, the tank could be used successfully in Omaha, however, they failed almost across the board.

The floating tank belonged to the so-called Hobart’s Funnies, which were specially developed for the invasion and the use of the beaches. Most of these units were from the British and Canadians used on their beaches, only the swimming tanks were taken over by the Americans. However, it is speculative whether a more extensive use of the other developments and a prudent use of the swimming tanks, especially at Omaha Beach, would have led to fewer losses.


Already during the First World War amphibious tanks were tested, but since none of these vehicles worked reliably, they were not used.  In the inter-war period was the further development in this field.  Basically, two types were distinguished by amphibious tanks:

Armored vehicles with natural buoyancy – but they were too small or the other of size so bizarre that a use was not an option.

Armored vehicles with mounted floats – but they fit with their size in no landing ship.

1941 sparked Nicholas Straussler the problem by water-repellent canvas zusammenbaute to a folding screen that the mood of buoyancy tanks without them zulegten considerably in width.  However, this process was operational only in calm waters.  The British Major General Percy Hobart proven Strauss Jewellers Folding successfully Valentine – and Tetrarch -tanks.  The Valentine tank went into production and were thus used in the wake of the Allied tank crews for landing training.  It also led to fatal accidents over again.

1944 turned out that the American Sherman tank is much better suited to swimming ability and conversion.  A great advantage of the Sherman was the direction the cannon ahead.  He was ready to fire immediately after landing.  In addition, the Valentine tanks significantly older and the Sherman was inferior in fighting power.

For the use of the DD Sherman tank of the tanks were sealed tub and two extra rear drive propeller attached, which the transmission could be switched on the carapace.  Then there was the case of swimming Straussler.

The swimming tanks were by driving two propellers in the water about 7 km / h fast.  The control was done by means of rotation of the propeller and a rudder .  The floating cover consisted of a line screen, which could be established by means of rubber hoses 36.  They were filled with air and gave the linen shade the necessary rigidity.  The floating cover was fixed with a metal frame above the chain cover to the outer skin of the tank.  The pumping lasted about 15 minutes.  The folding was significantly faster to make use of the ability of the tank on the beach.

The British tried the Cromwell – and Churchill tanks to equip accordingly.  But this could not be completed.  The British post-war tank Centurion was tested with a life jacket and a duplex drive.  Towards the end of the 1950s the development of DD tanks was set because the newer tanks were too heavy to give them buoyancy.  Light tanks were swimming but in China, produces, and some other nations also developed amphibious vehicles, but no tanks.

Even the German Reich developed for use during Operation Sea Lion Swimming tanks from the same intention as the Allies out their DD tanks. Thus, the immersion Panzer III was a modified version of the Panzer III and how was the DD tank be launched from a landing craft about one and a half kilometers from the beach.  Unlike the floating tanks of the Panzer III went diving on the sea floor (underwater driving).  A rubber hose supplied the engine and crew with air.  He reached a maximum depth of about 15 meters.


The main use of DD tanks was during Operation Neptune on D-Day, instead.  A small number were also in operation Plunder, the Rhine crossing at Rees and Wesel established in March 1945.

Ten tank battalions of Americans, Canadians and Britons were fitted before the Normandy landings with swimming Sherman tanks.  Special landing craft (LCT), each loaded with four tanks, should approach down to the coast with its load down to about three kilometers and let the tanks there to water.  This should then swim to shore and surprise the German defense, which was not set to a tank attack.  During the battle, the use of the swimming tank was partly successful, partly he failed, however – the latter mainly at Omaha Beach.

The British Sword Beach, at the eastern end of the invasion zone, the swimming tank worked very well, since there the sea was relatively calm. The DDs were exposed to about four kilometers from the beach. 32 of 34 swimming tanks reached the shore where they could support the landing troops on schedule.  That they contributed significantly to the relatively low number of casualties there.

The lake at Gold Beach was much troubled, as was decided that the DDs to bring directly with the boats on land and not at sea before they suspend.  Therefore, they were not the first units on the beach, but came with the invasion troops.  In some sections, the Germans managed to deal with anti-tank missiles several DDs out of action.  The application was on the whole successful.

The Canadians were able at Juno Beach only to have some of their tanks at sea and swimming to land.  The DDs started swimming at a distance of approximately 700 meters to the shore.  For this reason, they arrived after the first wave of soldiers who suffered heavy losses.  The tanks were able, however, to fight the German defensive positions successfully, so that Canadians could quickly advance a few kilometers inland.  At the east end of the lake Juno Beach was still rough, so the Canadians landed there were no tanks on the banks what they cost many victims.  Nevertheless, they made a breakthrough.

On Utah Beach, four swimming tanks were lost when their landing craft hit a mine, exploded and sank.  The remaining 28 reached the shore harmless, but about a quarter of an hour after the faster the infantry landing craft.  Here, too, wore their use to the low losses at this American landing in section.

The highest rate of loss had the swim tanks when used at Omaha Beach suffered because there were lost without exception all vehicles. 27 DDs were still driving while under the sea.  This is generally attributed to the underrated and very angry sea. The wave height for which the cover was built, should normally not be more than 0.3 meters.  On this day, however, the wave height was almost two meters in front of Omaha.  Under these conditions, the crews had never trained, and the sheath quickly filled with overflowing water.  In addition, the tanks were left far too early to water.  The distance to the shore was still nearly five kilometers.  Given the difficulties to control a 35-ton tank converted, it’s amazing how far the DDs came despite the odds.  Ultimately, however, all crews were drowned in their cars. Them available respirators submitted for only five minutes, which was too short in view of the rough sea. Some tried to warn the later starting tank crews over the radio that they should start closer to the shore.

Recent studies assume that the Omaha DDs targeted as a destination Steeple on the horizon behind the cliffs of Omaha. To maintain the line of sight, seemed to have the swimming tank due to the prevailing flow quickly aligned parallel to the beach.  The high waves could then penetrate the shell floating in the interior and fill the tank.  Had they remained true to their original orientation, they would succeed in getting through to the beach.  Other opinions are based on a self-protection of the ship’s commander, who saw their ships with too large coastal areas at risk and as the swim tank exposing too early.

DD tanks today

In the Bovington Tank Museum in England still intact Sherman and Valentine tanks are swimming pool with working envelope.

Three of the D-Day submerged tanks were lifted in the 1970s.  One is at the Musée des épaves Sous-Marine du Débarquement (Museum of Underwater Wrecks of the Invasion), a private museum in Port-en-Bessin issued in Normandy.  Another is at the Juno Beach Centre, the Canadians gewidmetem a D-Day museum in Courseulles-sur-Mer.

In 2000, the attempted U.S. Navy, a lower DD tank at Salerno in Sicily to lift, but failed.

amphibious tanks today

The tanks and battle tanks used today can be classified into several categories:

Tanks that can pass under rivers and streams through shallow breathing tube attached

Tanks, for the river crossing on ferries or bridges of the pioneers are instructed

Light tanks, due to their specific weight without buoyancy aids floats are

Tanks that need an extra boost, such as an attached float, for example K21 NIFV

anks to the DD principle, such as the Swedish S-tank

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