The DD Tank is commonly used to refer to amphibious tanks used in the Battle of Normandy, they were predominately American M4 Sherman medium tanks adapted to allow them to travel on water and land. It is so named after it's "duplex drive" system. The word amphibious or amphibian, when used alone, has several possible meanings in the English language. ... Battle of Normandy Conflict World War II, Western Front Date June 6, 1944 – August 25, 1944 Place Normandy, France Result Allied victory The Battle of Normandy was fought in 1944 between the German forces occupying Western Europe and the invading American, British, and Canadian forces. ... American, when used as an adjective, can mean of the United States of America or of or relating to the Americas; when used as a noun, United States citizen, residing in the Americas, or less frequently American English. Immigrants to the United States are usually called first-generation Americans, regardless... General characteristics Length: 5. ...

The DD tank was required to provide infantry support on the beaches. By giving the tank the ability to float, it could be launched from a landing craft and make its own way onto the beach. Having tanks on the beaches would have created an advantage for the allies, as the German defences were designed to protect against troops and were not expecting mechanical weaponry. The tank was successful at Juno Beach but failed the Americans on Omaha Beach. Infantry in the First World War Infantry (or Infantrymen) are soldiers who fight primarily on foot, using personal weapons. ... In general, allies are people or groups that have joined an alliance and are working together to achieve some common purpose. ... The word German can mean: From or related to Germany or its predecessor states - see also the German language Germanic tribes Holy Roman Empire (843-1806) German Confederation (1815-1866) North German Confederation (1867 - 1871) Germany, the modern nation-state founded in 1871 When used to denote a person, Germans... Juno Beach was one of the landing sites for Allied invaders on the coast of Normandy during D-Day, the invasion of Normandy on June 6, 1944, a turning point of World War II. It was situated between Sword Beach and Gold Beach. ... Troops from the first division landing on Omaha beach Omaha Beach was the Allied codename for one of the principal landing points during the Normandy landings on June 6, 1944. ...

The DD tanks were one of the many specialised assault vehicles known as Hobarts funnies that were offered to American forces for the invasion, but the DD were the only ones adopted. It has been speculated that if the DD were better used, or some of the other vehicles had been used that American losses on the beaches of Normandy, particularly Omaha beach would have been far less. Hobarts Funnies were a number of unusual modified tanks designs that were built by the unit 79th (Experimental) Armored Division Royal Engineers under the leadership of Percy Hobart whom the tanks were named after. ... Mont Saint Michel is a historic pilgrimage site and a symbol of Normandy Normandy is a former country (a Duchy) situated in northern France occupying the lower Seine area (upper or Haute-Normandie) and the region to the west (lower or Basse-Normandie) as far as the Cotentin Peninsula. ... Troops from the first division landing on Omaha beach Omaha Beach was the Allied codename for one of the principal landing points during the Normandy landings on June 6, 1944. ...

There were other amphibious tanks, both before and after the Sherman used in World War 2, however the later ones were chiefly experiments as tanks were so heavy. The DD Tank was designed specifically for the Normandy invasion. German soldiers at the Battle of Stalingrad World War II was the most extensive and costly armed conflict in the history of the world, involving the great majority of the worlds nations, being fought simultaneously in several major theatres, and costing tens of millions of lives. ...

Development

The amphibious tanks were tested during the First World War, but none worked well enough to use in combat. There was still development of them leading up to the Second World War, they were generally of two kinds; Some with natural buoyancy, these were generally either to small to be useful or so large as to be impracticably bizarre. The other kind were normal tanks with floatation added on, these were too big to fit onto landing craft. Ypres, 1917, in the vicinity of the Battle of Passchendaele. ... In physics, buoyancy is an upward force on an object immersed in a fluid (i. ...

In 1941 Nicholas Straussler solved the problems faced by other amphibious tanks by inventing the folding screen which was made of waterproofed canvas, this made tanks buoyant while not adding much size. canvas, see canvas (disambiguation). ...

British Major General Percy Hobart applied Nicholas Straussler’s folding screen design to Valentine and Tetrarch tanks. Hobart first tested the folding screen with a Tetrarch tank in Portsmouth Harbour. The test was successful and production was started using the Valentine tank. The majority of the American, British and Canadian DD tank crews did their preliminary training on the Valentine DD and there were several training losses using the Valentine. Sir Percy Hobart (1885-1957) was British military engineer and commander of the 79th Experimental Armored Division during the World War II. Many of his contemporary superior officers mainly tried to disregard him. ... The most heavily manufactured British tank in World War II, the Infantry Tank III Valentine was known mainly for its inexpensive cost and high reliability. ... This article is about the English city of Portsmouth. ... The word British has several different uses. ... Canada is the second largest country in the world in land area, and the northern-most, occupying much of the North American land mass. ...

Weighing around 35 tons the DD Sherman lay low in the water. On one hand it wasn't very noticeable but on the other the top of the screen was barely above the water.

By 1944, it was clear that the Sherman tank was more suitable for amphibious use than the Valentine, one reason was that it could move in water with its gun forward ready to fire as soon as land was reached. The Valentine was also an older and generally inferior design. Modifications to the Sherman included; sealing of the lower hull, the addition of two propellors to the rear of the hull driven fom the engine gearbox and the addition of Straussler's flotation skirt around the hull.

DD Tanks could move at up to 4 knots with the propulsion provided by the pair of propellers. The tanks were steered in the water by directing the propellers and a rudder. The flotation screen was a canvas curtain supported by thirty-six rubber tubes. These tubes were inflated with air to give the curtain rigidity. The canvas was attached to a metal frame welded to the tank's hull. The screen could be inflated in 15 minutes, and quickly deflated once the tank reached the shore.

Designs were even made to give the Cromwell and Churchill tank the ‘DD’ treatment, but these were never finished. After the war the Centurion tank was tested with floatation screen and duplex drive. By the end of the 1950s development of swimming battle tanks had ceased, as they were becoming too heavy. Swimming armoured vehicles continued though in the floatation screen equipped British Abott self-propelled gun and the naturally bouyant Alvis Stalwart High Mobility Load Carrier (FV620). A27M Cruiser Tank VIII Cromwell was one of the most successful series of cruiser tanks fielded by Britain in World War II. It was the first tank in the British arsenal to combine a dual-purpose gun, high speed, and reasonable armor. ... The Churchill tank Infantry Tank IV Churchill. ... The Centurion was a British Main Battle Tank of the post-war era. ...

Combat

The DD Sherman was used to equip ten tank battalions of British, Canadian and American forces for the D-Day landings. In theory, the DD tanks were to be launched off landing crafts two miles offshore, swim to the beaches and overpower German defences unprepared to attach tanks. In reality, though, the tanks were a limited success. As they could not fire their main guns while the screen was raised, they were vulnerable to enemy fire up until they reached the beach. On D-Day, most were launched directly onto the beach without having used their floatation gear. At Omaha Beach almost all of the tanks launched offshore were lost, contributing to the high casualty rate and slow progress at that beach. Troops from the first division landing on Omaha beach Omaha Beach was the Allied codename for one of the principal landing points during the Normandy landings on June 6, 1944. ...

In total 27 tanks sank at sea. It is believed the sea was too rough. The DD Tanks were designed to withstand waves up to 1 foot high, on that day the waves were up to 6 feet high. These were much worse conditions than they had trained in and they were swamped with water. Also, the tanks were released into the sea too far out (about 3 miles offshore), combined with the inherent difficulty in steering a 35 ton modified tank it is a tribute to the crews that they got as far as they did. The tank crews drowned at sea. Although they were equipped with emergency breathing apparatus capable of lasting 5 minutes this was not nearly enough in the turbulent sea. Some did manage to radio back and warn following units not to launch as far out.

Until very recently it was believed that the DD Shermans that were launched offshore of Omaha beach (from 741st Armored Battalion) were mostly sunk immediately, swamped by the seas that were much higher than the operators had practiced with. It was suggested that they were launched too far from shore. However tanks at the other four beaches suffered no such problems. New research suggests that the Omaha tanks were aiming for a church steeple on the visible horizon behind the cliffs. In order to maintain their line of sight it is believed that the tanks had to turn progressively away from the shore to combat the wavefronts pushing them down the beach, putting their sides virtually parallel with the waves/beach. This meant that the protective canvas flotation devices were easily swamped by the waves. If they had kept going directly forward with the front of the tank headed straight for the beach, they may well have reached it.

References

• http://www.sproe.com/t/tank-dd.html 14 April, 2005
• http://www.d-daytanks.org.uk/articles/developing-tank.html 14 April, 2005
• BBC history 'D-Day - The Untold Story' (http://www.bbc.co.uk/history/archaeology/marine_dday_underwater_05.shtml) 14 April, 2005
• BBC news 'The tanks that didn't land on D-Day' (http://news.bbc.co.uk/1/hi/uk/2016280.stm) 15 April, 2005
• http://www.historylearningsite.co.uk/duplex_drive.htm 14 April, 2005