Duplex Drive Tanks

The Degree of Success and Effectiveness of Amphibious Duplex Drive Tanks During the Invasion of Normandy

            Before the Allied invasion of Normandy on June 6, 1944, a new and secret weapon was developed by the Allied forces that would change the face of amphibious assaults. This new weapon was the Duplex Drive amphibious tank, a medium tank fitted with a canvas screen and propellers that allowed it to float and move in water. Duplex drive tanks, colloquially referred to as DDs, were extremely helpful and effective in aiding the infantry on certain beaches during the D-Day invasion. However, many of the tanks sank before they could reach land due to poor weather and rough seas, particularly those destined for Omaha Beach, which proved to be an extreme setback. Duplex Drive tanks were simultaneously a great success and catastrophic failure depending on where they were deployed during the D-Day invasion.

            Before it is possible to assess the effectiveness of these specially designed tanks, it is imperative to understand their design and what they were made to accomplish. The Duplex Drive tank was part of a series of tanks referred to as “Funnies” conceived by the British Major General Percy Hobart.[1] This group of modified tanks included the Duplex Drive tank with its canvas flotation screens, and other specialized tanks fitted with mine-clearing flails, searchlights, portable bridges, and flamethrowers.[2] The Duplex Drive tank was the first truly amphibious tank, fitted with a canvas screen that, when erected, would transfer power from the tracks to twin propellers.[3] These modifications allowed the waterproof tank to stay afloat and propel itself forward in water. Once the tank reached land, the screens would be lowered which transferred power back to the tracks and converted the tank back into a land vehicle.[4] These amphibious modifications were tested on Valentine tanks, but the battle models were the Sherman M4 Medium Tank and the A22 Churchill Infantry Tank Mark IV for the American and British forces respectively.[5] In order to accommodate the new tank models which were significantly heavier than the Valentine, the canvas screens were increased to seven feet tall.[6] These specialized additions to the Medium tanks allowed for them to become amphibious weapons.

            However, the design of the DD would prove to be its downfall when landing on certain beaches during the invasion of Normandy. The canvas screens which provided the ability of flotation were easily torn if caught on other pieces of equipment.[7] Furthermore, if the sea was especially rough, the 7 foot tall canvas could easily be swamped by the waves resulting in the sinking of the craft.[8] If a landing craft passed too closely to the tank, it could be sunk as well, either due to a direct collision or overwhelmed by the wake of the LCT. Cases of carbon monoxide poisoning were even reported in test runs of the amphibious tanks due to fumes emitted from the developing weapon.[9] These design flaws, most notably that the canvas could be easily overtaken by waves, would contribute heavily to the loss of significant numbers of tanks, particularly on Omaha Beach.

            Despite their awareness of the potential problems with the DD tanks, the British forces were determined to implement their new weapon during the D-Day invasion. However, the American generals were wary of using these modified tanks. General Leonard Townsend Gerow thought the DDs were unreliable and instead favored delivering the tanks directly to shore by means of landing craft.[10] General Omar Bradley, also cautious of the new weapons, eventually consented to the use of DDs but denied the use of other specialized British tanks protesting that the American troops would not have adequate time to train.[11] Although the American forces accepted the DD tanks, many continued to criticize the decision, claiming that armor would not be desirable at such an early stage in the invasion and would prove to be more trouble than it was worth.[12] That is, the logistics involved with landing DD tanks ashore would work against the aims of the landings, hindering progress and congesting the beaches. Despite the concerns of the American generals, it was decided that the DD tanks would be implemented in their landing strategies.

            Before the DD tanks could be implemented, they had to be tested and the men had to be trained to operate them. Besides learning to pilot the armor, the most important part of training was the use of what was known as amphibious tank escape apparatus. Men would take their stations in a tank placed at the bottom of a well and wait for it to fill with water completely before activating the apparatus and escape.[13] This exercise simulated the high possibility that the tank would sink upon launch. The men also practiced driving the tanks into Fritton Lake, the base of training on the amphibious tanks in England. One training exercise ended with the sinking of seven tanks and the death of six men, which demonstrated the real dangers in implementing this technology. However, the fatal flaw of the training of men on the DD tank was that they were never tested in rough seas. If the weather was inclement, training would be cancelled. Had the troops trained with the DD tanks in rough seas, it is possible that the number of tanks that sunk would have been much lower due to experience in navigating such conditions or would lead military leaders to have chosen not to implement them at all.

            In terms of strategy, it was decided that the DD tanks would be launched from their landing craft about four miles from the shore. This far distance would allow the tanks to be far enough away from enemy fire, but conversely it increased the distance that the tanks would need to travel in the water.[14] Because of the amphibious nature of the tanks, they would be able to be employed early in the assault, providing initial fire to cover the following infantry.[15] Furthermore, the shock value of fully armed tanks driving out of the ocean was a key element of their strategy.[16] Years after the invasion, a German soldier remembered a tank “rolling towards us, from a direction in which we had not even suspected the presence of the enemy.”[17] This surprise illustrates one instance of success for the shock part of the Allied strategy. Considering the manpower of the Allied invasion, the British Army deployed three infantry divisions, one armored division, and three armored brigades, while the American Army deployed three infantry divisions, five tank battalions and two commando battalions.[18] Within these, a total of five hundred and fourteen tanks were launched during the invasion.

            On the morning of the invasion, it became apparent that the weather would be a problem for the launching of the DD tanks. There was an extreme wind and the tide rose half an hour before it was expected. [19] However, this inclement weather affected certain beaches more than others.  The British and Canadian landing beaches of Gold, Juno, and Sword were not as drastically affected by the weather, mostly due to the decision of the commanders that the DD tanks would be released closer or directly on shore.[20] This allowed the tanks to travel a shorter distance or no distance at all in the rough seas, greatly increasing the odds of reaching the beach. The American beaches, however, did not fare as well. Utah beach had difficulties with the weather but the commanders in charge also decided to launch their DD tanks closer to shore, saving the majority of them due to decreasing the travel distance.[21] However, the weather caused the majority of the DD tanks destined for Omaha beach to sink since commanders launched the tanks from the original four miles despite the poor conditions. Furthermore, the harsh terrain prevented the few that made it to shore from inflicting much damage.[22]

            On Sword beach the DD tanks were launched only 5,000 yards out to better ensure the success of the machines in reaching their destinations. [23] This change in strategy proved wise, as thirty-four of the forty tanks were launched from their landing craft successfully.[24] Furthermore, of those thirty-four, thirty-one reached the beach.[25] Two of the DD tanks that were launched successfully but failed to reach the beach were sunk due to being struck by nearby landing craft.[26] When combined with the duplex drive tanks that were delivered directly to shore, a total of forty seven tanks successfully made it to the beach.[27] On Sword, the tanks arrived before the infantry, as planned. The DD tanks that reached the landing zone effectively cleared the beach so that the infantry could also land and begin their portion of the assault.[28] However, this planned early arrival of the tanks was not the case on either Juno or Gold, the two remaining British and Canadian beaches.

            Due to poor weather and rough seas, the DD tanks were launched as close to shore as possible on Juno beach with some being carried all the way to shore by their landing craft.[29] Of the first wave of nineteen DDs launched, fourteen successfully made it to shore.[30] Once the tanks made their way up the beach, they immediately began firing on the defensive positions of the enemy.[31] In addition, they began to clear the beach of obstacles so the remaining infantry and other forces would be easier able to invade.[32] However, had the tanks arrived earlier, it would have easier for the leading infantry to begin to infiltrate the enemy positions and make their way inland. This was similarly the case on Gold beach.

             Not only did the DD tanks destined for Gold beach arrive behind the majority of the infantry, but they also had problems once they arrived. Some of the 4th and 7th Dragoon Guard tanks could not maneuver over areas of soft sand, a condition that had not been accounted for during training, becoming immobile and eventually overcome by the incoming tide.[33] Other DD tanks were hit by enemy fire soon after landing, disabling them. However, the shot tanks proved to be a blessing in disguise for portions of the infantry who used the disabled tanks as temporary cover.[34] B.T. Whinney, a Gold beach soldier, related that “the disabled tank was a great boon to us, because it gave us a narrow kind of shelter from the fire from the pill box.”[35] He, along with other solders, rationalized that the enemy would not waste further ammunition and firepower on a machine already taken out of action.[36] While the DD tanks of Juno and Sword were extremely effective for providing cover for the infantry once they arrived, a majority of the tanks reached shore after the troops did. This defeated their purpose of providing the initial firepower support so that the infantry would not take the brunt of the enemy fire.

            Unlike Juno and Gold beach, the American beach Utah saw the successful deployment of their DD tank units ahead of the infantry. However, the landing was not without difficulty or incident. The weather continued to pose a problem, and therefore the tanks were launched only two miles from shore instead of the planned four.[37] Furthermore, four of the thirty-two duplex drive tanks that were launched were lost when their landing craft struck a mine.[38] Sam Gauthier, a soldier who witnessed this event remembers that the explosion “immediately set up a state of confusion…An LCT with the four DD tanks had just been blown sky high and everything just disappeared in a matter of seconds.”[39] However, despite the revised launch distance and the confusion following the loss of four DD tanks, twenty eight of the thirty two tanks arrived on the shores of Utah.[40] These tanks that made it ashore were not only extremely effective in providing initial firepower and cover for the infantry but also in creating an approach route that would allow reinforcements and other equipment to make their way inland as maintained by Olivier Wieviorka.[41] The terrain of Utah beach, which consisted of a low incline and no obstructing bluffs, allowed the DDs to have an easier time coming ashore and allowing for the movement off the beach. However, Omaha, the other American landing beach, did not have that luxury.

            The landing of the DD tanks at Omaha beach was dramatically more difficult than any other beach in the entire invasion due to its incredibly poor terrain and landscape. Within the sea were a great number of large rocks, making the waves choppier which negatively affected the tank landing. Furthermore, the entire beach was bordered by one hundred foot cliffs, with a pebbly stretch of dunes in the center. Beyond the dunes was a salt marsh ending in deep ravines.[42] This terrain also proved to be a tactical disadvantage, as the enemy held the fortified high ground.[43] Despite this terrible landing zone, the American forces still decided to send battalions of duplex drive tanks to support the infantry’s invasion.

            It was decided that a total of 64 DD tanks would be launched destined for Omaha beach with 32 each belonging to the 741st and 743rd battalions.[44] However, the majority of these tanks never reached shore and the ones that made it did so behind the infantry.[45] One contributing factor to this tragedy was that the American command on Omaha decided to launch the tanks from the original four miles instead of augmenting the plans to account for the weather.[46] Due to this extreme miscalculation, the entirety of the 743rd battalion sank as the canvas flotation screens of the tanks were overwhelmed by the choppy waves.[47] What is striking about this fact is that these tanks were launched one after another so that the soldiers saw each tank before theirs sink.[48] Perhaps it was the patriotic rhetoric used by Dwight Eisenhower in his speech to the troops before the actions of D-Day that inspired them to follow the doomed tanks. Eisenhower referred to the deployment of soldiers as “the Great Crusade” and claimed that “the free men of the world are marching together to Victory!”[49] Whether it was idealistic motivation or simply the failure of the soldiers to properly analyze what they were about to do, the soldiers actions demonstrated a determined resolve.

            The 741st battalion had more success than the 743rd, but not by much. Of its thirty-two DD tanks, only two made it to the beach by their own power.[50] However, according to Everett Schultheis, a man in the Omaha infantry, the two tanks were knocked out by hostile fire immediately after coming ashore.[51] Three more were deposited directly on the beach from their landing craft however the remaining twenty-seven never reached shore.[52] These surviving DD tanks combined with two companies of regular Shermans delivered by landing craft were the only support for the infantry.[53] Although the trek to the beach was extremely difficult, the assault on the beach itself proved to be no easier for the DD tanks.

            Once ashore, the tanks had to overcome the terrain. Many tanks were swamped by the soft sand and others were taken out of action immediately by hostile fire.[54] Furthermore, there were only three ways for the tanks to get off the beach through the unforgiving bluffs.[55] Few avenues of moving inland and the poor terrain of the beach itself caused terrible congestion and confusion of the tanks.[56] One soldier, Martin Sommers, claimed that “tanks and infantry seemed to be milling around aimlessly.”[57] Soldiers resorted to using disabled tanks as shields from enemy fire, similarly to those on Gold beach.[58] The DD tanks that did survive the journey to shore and up the beach provided support for the infantry in taking out enemy machine gun nests and killing a great amount of enemy infantry.[59] However, the paltry amount of tanks were not enough to truly make a difference in protecting their infantry which is one of the key reasons there were so many casualties on Omaha beach. Furthermore, because of the poor terrain, Omaha was the beach that needed the support of the DD tanks the most and tragically did not receive it.

            However, this one tragic beach did not define the performance of the DD tank overall. Certainly, on the British beaches the DD tanks provided key support to the infantry to begin their invasion. On the American beach Utah, the duplex drive tanks also effectively landed and aided their infantry in their assault against the enemy.[60] Assessment of the DD tanks is important to understand because without the DD tanks it is possible to suggest that the invasion would have been much more difficult, and indeed this was apparent on Omaha beach.[61] The use of this weapon contributed to the success on the majority of the beaches and the lack of this weapon contributed heavily to the near failure on others. Despite the role the duplex drive tanks played in the invasion of Normandy, all of the tanks that sank remain at the bottom of the English Channel.[62]


[1] George Forty, Tanks of World War I and II, (London: Anness Publishing Ltd, 2006), 24.

[2] Ibid.

[3] Martin Gilbert, D-Day, (Hoboken, NJ: John Wiley and Sons, Inc, 2004), 41.

[4] Robert M. Citino, Armored Forces: History and Sourcebook, (Westport, CT: Greenwood Press, 1994),  95.

[5] Major-General Charles H. Miller, History of the 13th/18th Royal Hussar (Queen Mary’s Own) 1922-1927, (London: Chisman, Bradshaw, Ltd, 1949)

[6] David Fletcher, Swimming Shermans: Sherman DD Amphibious Tank of World War II, (Oxford: Osprey Publishing Ltd, 2006), 15.

[7] Adrian R. Lewis, Omaha Beach: A Flawed Victory, (Chapel Hill: The University of North Carolina Press, 2001), 99.

[8] G. M. Giangreco and Kathryn Moore, Eyewitness D-Day: Firsthand Accounts from the Landing at Normandy to the Liberation of Paris, (New York: Union Square Press, 2004), 132.

[9] Adrian R. Lewis, Omaha Beach: A Flawed Victory, (Chapel Hill: The University of North Carolina Press, 2001), 99.

[10] Ibid, 172.

[11] John Mosier, The Blitzkrieg Myth: How Hitler and the Allies Misread the Strategic Realities of World War II, (New York: Harper Collins Publishers, 2003), 219.

[12] Christopher D. Yung, Gators of Neptune: Naval Amphibious Planning for the Normandy Invasion, (Annapolis, Naval Institute Press, 2006), 213.

[13] Fletcher, Swimming Shermans, 11.

[14] Yung, Gators of Neptune, 120.

[15] Ibid., 95-96.

[16] Ibid., 162.

[17] “The Normandy Invasion, A German Soldier’s Point of View,” Eyewitness to History, www.eyewitnesstohistory.com (accessed February 2, 2012).

[18] Olivier Wieviorka, Normandy: The Landings to the Liberation of Paris, (Cambridge, MA: Harvard University Press, 2008), 185-186.

[19] Ibid., 190.

[20] Ronald J. Drez, Voices of D-Day: The Story of the Allied Invasion Told By Those Who Were There, (Baton Rouge: Louisiana State University Press, 1994), 290.

[21] John Man, The Facts on File D-Day Atlas: The Definitive Account of the Allied Invasion of Normandy, (New York: Harper Collins Publishers, 2003), 44.

[22] Lewis, Omaha Beach, 90.

[23] Yung, Gators of Neptune, 180.

[24] Ibid.

[25] Ibid.

[26] Max Hastings, Overlord: D-Day and the Battle for Normandy, (New York: Simon and Schuster, 1984), 104.

[27] Wieviorka, Normandy, 199.

[28] Hastings, Overlord, 103.

[29] Yung, Gators of Neptune, 181.

[30] Wieviorka, Normandy, 198..

[31] Yung, Gators of Neptune, 181.

[32] Giangreco and Moore, Eyewitness D-Day, 180.

[33] Fletcher, Swimming Shermans, 23.

[34] Drez, Voices of D-Day, 288.

[35] Ibid.

[36] Ibid.

[37] Ibid., 44.

[38] Giangreco and Moore, Eyewitness D-Day, 132.

[39] Drez, Voices of D-Day, 173.

[40] Hastings, Overlord, 87.

[41] Wieviorka, Normandy, 196.

[42] Man, The Facts on File D-Day Atlas, 46.

[43] Lewis, Omaha Beach, 106.

[44] Ibid., 97.

[45]Hastings, Overlord, 90.

[46] Ibid.

[47] Ibid.

[48] Ibid.

[49] Carl Spaatz Papers, Churchill and the Great Republic Collection, The Library of Congress.

[50]Giangreco and Moore, Eyewitness D-Day, 133.

[51] Drez, Voices of D-Day, 251.

[52]Fletcher, Swimming Shermans, 23.

[53] Giangreco and Moore, Eyewitness D-Day, 133.

[54] Drez, Voices of D-Day, 283.

[55] Lewis, Omaha Beach, 254.

[56] Drez, Voices of D-Day, 251.

[57] Ibid.

[58] Ibid.

[59] Giangreco and Moore, Eyewitness D-Day, 133.

[60] Yung, Gators of Neptune, 213.

[61] Fletcher, Swimming Shermans, 43.

[62] Lewis, Omaha Beach, 255.

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