Duplex Drive Shermans
Due to the limited nature of available reference sources, some of the information presented here must be considered as "educated guesswork".


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DDs were used on a much smaller scale in several more operations in Europe. Each required a considerable amount of crew training beforehand. For Operation Dragoon, this was conducted at the Invasion Training Center at Salerno, Italy. Starting on July 10 1944, crews received about 30 days of instruction from a British DD team sent from England. The DDs arrived somewhat later, and in the meantime, crews practiced various swimming techniques with DUKWs. Escape drills were conducted using a giant vat located in a warehouse in the nearby town of Battipaglia. Crews were to remain in the hull of a salvaged Sherman, as the vat was flooded with water to 18 feet. They then evacuated the tank with the aid of a "Monson Lung" device. With the arrival of the DDs, crews received about 18 hours of instruction in LCT launching and 12 hours in beach operations. Two DDs were lost with one fatality when their screens were ripped "by a projection on the ramp of an LCT" just as they launched. The small hatch M4A1 DD at Piana Dell Orme would be one of these, and there may still be another on the seabed off  Salerno.


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The 191st, 753rd and 756th Tank Battalions had trained personnel sufficient to operate 16 DDs each during the invasion. Only 36 were actually used due to "LCT loading space available". It is thought that the 48 DDs sent to Italy all came from the group of 76 unused M4A1s that remained in the UK after D-Day "with no operational need at this time". Unlike the Normandy Invasion, the Mediteranean Sea was calm on August 15 1944, and the table above shows the outcome for Operation Dragoon.


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DDs were used in several river crossing operations in 1945 in both the European and Mediterranean Theaters. In one example, C Company of the 736th was attached to the 743rd Tank Battalion. Due to his prior experience, William Duncan, now a Lt. Colonel and commanding officer of the 743rd, supervised the crossing of the Rhine by the DDs of C Company on March 24 1945. DDs required a suitable landing place on the far shore, and one was located near the town of Ork, and improved by engineers about an hour beforehand. The first DD crossed at 0345, and all 17 made it across safely by 0554. They then "marched to the sound of the guns" in support of the 30th Infantry Division, which had preceded them in the assault. It is to be noted that elements of Col. Duncan's 743rd crossed the Rhine near Wallach, ferried by two Bailey rafts, later that same day. Some of the DDs used by US units for the Rhine crossings were British conversions, such as the Sherman III (M4A2) DD pictured above. Based on the road sign locations, this DD is thought have been with the 748th Tank Battalion. The battalion had 51 DDs, but only a small number were still "floatable," due to wear and tear. One sank immediately upon entering the water because of a torn screen, but 7 of their DDs managed to swim across the Rhine at Oppenheim on March 23. Photo courtesy of Recon Military Photos.


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The records emphasized the importance of a good landing place on the far shore during river crossing, and mention that a couple of the 736th's DDs missed the "ramp", but were able to turn around and make a second attempt thanks to the slow current that day. The photo sequence above shows a similar mishap involving USA 3070200 of the 781st Tank Battalion. The crew, which was training on the Neckar River in April, overshot the landing ramp and dropped the DD's "sides a trifle soon". The crew averted disaster by re-inflating, backing off and coming back in for a successful landing. By the USA Number, this tank would have been made by Pressed Steel Car, and accepted in November, 1943. It can be seen to have "small" drivers' hatches, along with an improved low bustle turret with factory installed loader's hatch. The DDs would have been over a year old by then, and one can see the extensive patching of the canvas.


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The British Sherman DD conversion program ended in December 1944 after 693 units had been produced. This would seem like a sufficient number for training and further amphibious Operations after D-Day. However, they ordered an additional 300 US produced DDs as part of their 1945 Lend Lease requirements. These were offered to them based on the M4A2(76)HVSS, since that was the only Sherman being built for Lend Lease at the time. This was negotiated down to 200 units, and two pilot models (British nomenclature "Sherman IIIAY DD III") were completed in the Summer of 1945 at the Firestone Plant in Burlington, North Carolina. Production was scheduled at 50 per month starting in September, but the program was terminated due to the end of the war. One of the pilots was retained by the Ordnance Museum at Aberdeen Proving Ground for historic purposes, and was on display there for many years. It is S/N 69278, accepted in May 1945, the final month of Fisher M4A2 production. It is now thought to be in storage at the Anniston Army Depot in Alabama. Both photos courtesy of Neil Baumgardner.


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The Sherman IIIAY DD III had a higher screen than earlier models, so the tiller (item 1) and the steadying bar (item 2) were extended, and the commander (pilot) stood directly on top of the turret. Note the addition of armor skirts to protect the suspension (item 3). Major Duncan and his staff had suggested that on future designs "a cutwater or tin shield be added so vehicle may ram [underwater obstacles] without serious damage to itself." This was never incorporated, and leads us to suspect that, under most swimming circumstances, a crewman may have been stationed forward as lookout. Standing on the front support crossbar in order to see over the screen, he would have warned of any obstacles in the water that might endanger the canvas.


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The British continued development work on the DD into 1946. At some point, they improved the initial design to the "late DD I standard." This included the addition of turret struts, self locking struts and the extension of the rear screen. The turret mounted struts are rare in period photos, but can be seen on the 44th Royal Tank Regiment DD above. It was photographed on March 25, 1945 following Operation Plunder, the crossing of the Rhine by the 21st Army Group. Some Sherman III DD MK Is were redesignated MK IIs when they were fitted with conversion kits, which included the addition of power steering and an air compressor.


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The "Topee," was a hinged armored cover that protected the canvas screen when in the down or traveling position. This was designed in response to user recommendations after many screens had been torn when they brushed against various objects on the road. Concurrently, tests were conducted whereby remotely controlled machine guns and / or recoilless rifles were mounted at the top of the screen frame to give DDs some firepower when swimming in. While both of these modifications were recommended following trials, it is not thought that either went into production. Note that the Sherman III DD pictured on the left is built to the late DD I standard as evidenced by the turret mounted struts.


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British planners felt that an Armored Personnel Carrier was needed for future amphibious operations, and that the unarmored US built LVT and DUKW amphibians were not suitable for the assault role. They created an APC DD by removing the turret from a Sherman DD and replacing it with "a mushroom-shaped cover...raised above the turret ring to provide an all-round firing slit." It may have been intended to employ large numbers of APC DDs in future operations against the Japanese homeland. These would have been converted from existing stocks of DDs, and may explain why the British ordered 300 DDs from the US for 1945. The drawing above is speculative. The photos were missing from the APC Report in the Hunnicutt files, formerly at the Patton Museum. If any readers have APC DD images, we would be pleased to have the opportunity to see them.


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The DDs were no longer a secret after D-Day. Another British design, referred to as "Counter DD Equipments", "enabled DD tanks to swim through a sea of fire" should the enemy attempt to create such a defense. A series of nozzles were plumbed around the top of the screen, and misted the canvas with sea water, thereby preventing it from catching fire. Also known as the "Belch Apparatus", it appears to be the only British modification that actually went into production. Correspondence dated August 2 1945 states that "120 sets were ordered in May 1944 and were completed". It was further noted that there were 86 DDs in India, with plans to send over 100 more, presumably for the invasion of Japan. It was intended to equip all of these with the Counter DD modification, and was noted that the design would not fit the 200 US made DDs the British had ordered. These activities apparently ceased with the surrender of Japan.


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The period photos above show that at least two former British Sherman V DDs ended up in the 1st French Army. It is thought that they were part of the 351 Shermans transferred by the British to the US in January 1945 to make up for losses suffered during the Battle of the Bulge. For the most part, US units did not use the 120 M4A2s and 53 M4A4s sent, but held them as emergency reserves in the event that standard replacement types from the US were delayed. Once the crisis passed, many of these were transferred to the French whose armored units actually employed M4A2s and M4A4s. As with many used DDs, these tanks were stripped of most of their fittings so that they could serve more efficiently as regular gun tanks. Note the welds on the differential housings, and along the hull sides, as well as the raised headlamps and the power take offs from the DD idler wheels. The two tanks have been identified by Claude Gillono as with the 1er Régiment de Chasseurs d'Afrique, 5th French Armored Division, near the German-Austrian border in April 1945. A British WD Number can be seen painted on the turret of "France II". Photos courtesy of Claude Gillono - The French Shermans of the Libération 1944-1945.


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A French Army, ex British Sherman V DD has survived, and is currently displayed in Rixheim, France. This tank was used by the French in the post war years, and the original differential housing, gun mount and idler wheels appear to have been replaced, most likely during the "Transformé" upgrade. However, the hull and turret still clearly show the remains of Duplex Drive fittings. While the British T-Number is not known, paint deterioration has exposed the original USA Number, 3016910, painted on in blue drab. Both photos courtesy of Antoine Misner.


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There have been a few myths put forth about US DDs over the years. For instance, "M4A1 DDs with large drivers' hatches were built as M4A1(76)s, but 75mm turrets were retrofitted, because the 76mm would not fit inside the DD screen". This was circulated before it was discovered that Pressed Steel Car made about 100 large hatch M4A1(75)s in December 1943. Because they were recently produced, they were unallocated and therefore available for the DD conversion program. Of the 350 US DD conversions, the two pilot models, Serial Numbers 37844 and 37851, were ordered placed in secure storage at Lima Tank Depot "for possible future development work." By the serial numbers, these would have been large hatch, 75mm M4A1s. One, as seen above, was used to illustrate the DD Technical Manual. Note the early version of the M34A1 gunshield with lifting rings. Unlike other builders, Pressed Steel Car appears to have used these interchangeably with the later version right until the end of M4A1(75) production. 


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Speculation had it that all of the large hatch 75mm M4A1s were converted to DD. However, at least 6 unconverted units were used in various GMPG, APG and Armored Board Test Programs. There is one surviving example that shows absolutely no evidence of any DD fittings, and there are period photos of a large hatch M32B1 retriever in service in the ETO in Summer 1945. Large hatch 75 & 76mm hulls are very similar. The best way to tell them apart is that the 75mm hulls have cast in appliqué on the sides, since they "still" had the ammunition racks up on the sponsons, whereas M4A1(76)s incorporated wet stowage, which repositioned the ammo racks to the floor, and thus did not require cast in appliqué. The hull castings also have different part numbers - E8550 for the 75mm & E8595 for the 76.


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The large hatch M4A1 DD at Saumur "partakes" of the turret swap myth in that it has a 76mm turret. Some have speculated that it is not a real DD, but was mocked up for the film "The Longest Day". Our examination found that it has 75mm ammo bins and an E8550 upper hull casting. It is definitely real. Unfortunately, the serial number has been lost to time. A staffer at Saumur reported that the US provided the DD to the French Army after WW II for examination and test purposes. When it was transferred to the Museum in the 1970s, it was missing its original "high bustle" 75mm turret. The Museum retrofitted the 76mm turret simply to make the tank look complete.


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Another myth was  "All US DDs had turrets with loader's hatches". This appears to have come about because all of the known surviving examples have loader's hatches, and the hatches can be seen in a number of period photos. As mentioned in a previous caption, "Major Duncan recommended that all future units be equipped with large drivers' hatches, loader's hatches and pistol ports". This, of course, implies that all of them did NOT have these features. Pressed Steel Car introduced the oval loader's hatch into production around the end of October 1943. The majority of the 350 M4A1s converted to DDs came from the last few month's production at PSC. Thus, many of the DDs did have factory installed loader's hatches on either low bustle or high bustle D50878 turrets. PSC also introduced the cast in appliqué on the hull sides around this same time, so many DDs had that feature. However, not all the DD conversions came from late production PSC M4A1(75)s.  Some Lima Locomotive Works (LLW) and Pacific Car and Foundry (PCF) M4A1s were also used, but since those companies left the Sherman program in September and November respectively, the government did not mandate that they introduce the loader's hatch, large drivers' hatches or cast in appliqué improvements. Lima, PCF and any earlier PSC M4A1 conversions would have such features as "no pistol port" turrets, or "patched" turrets with welded up pistol ports, and hulls with welded on appliqué plates. A few examples are shown above.


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Not exactly a myth, but we have seen a few models that show M4A1 DDs with 3-piece or early one-piece differential housings. In late December 1943, the supply of unused, unallocated M4A1(75)s would have been limited to units produced in the last few months. The Government had mandated that in September 1943, all US produced Shermans transition to the late type of transmission and final drive. This leads us to believe that most or all of the M4A1 DD conversions would have had the sharp nosed or E8543 type of differential housing. These have been seen in the early configuration with cast in steps (above left), as well as the later form with welded on steps.


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