During World War Two the 79th Armoured Division, led by Percy Hobart were set the challenge of developing a range of specialised tanks. These were conventunal tanks modified to undertake secondary roles to combat the German Defences at Normandy. The amphibious swimming tanks (known as Duplex Drive or DD for short) were developed to provide close fire support to the first waves of infantry on D Day. The DD tanks were made to float by waterproofing the hull, fitting a collapsible screen that provided buoyancy (based on displacement theory) and rear propellers that provided propulsion when water borne. Their development can be attributed to Hungarian designer, Nicholas Strasussler.
In 1943 a series of Top Secret Training Wings were established to facilitate the training of the crews who would ulitmately take these tanks across the Channel. Fritton Lake in Norfolk became the Freshwater Training Wing, whilst Stokes Bay, Gosport, Hampshire the location of the Saltwater Training Wing. Over 1200 men attended courses at these locations, operating Valentine DD tanks.
The intention on D Day was for 240 Sherman Duplex Drive Tanks to launch 5000 yards from the Normandy Coast, out of range of the German guns, and to arrive on the beaches minutes ahead of the infantry to provide armoured support. Unfortunately the sea conditions were much worse than the crews had trained in, which lead to the varied outcomes on June 6th 1944. Never before had tanks supported the infantry so early in an amphibious assault.
Despite the poor weather on D Day over half the DDs were launched into the Channel, at distances off the Normandy Coast of between 750 yards and 5000 yards. A third of these were lost to the sea due to the bilge pumps being unable to cope with the water coming over the screens. However those tanks that did swim to the shore provided significant armoured and moral support to the Infantry. The successes of the Tanks during DDay resulted in the DDs being subsequently trained at a River Crossing Training Wing at Burton-upon-Stather, and utilised for further amphibious including the Crossing of the Rhine.
This website is being developed in assosciation with a forth-coming publication about the history and development of the Duplex Drive Tanks by Stuart Burgess, former Manager of Fritton Lake Country Park.