| Organisational History |
U.S. Special Armour units were developed from British Special Armour. Duplex Drive tanks, known to many American troops as Donald Duck tanks, are modified M4 Sherman medium tanks fitted with a collapsible canvas screen and rear propellers. These devices allow the tanks to float and move through water. The system is developed in Britain during the Second World War. It is created by the Hungarian-born engineer Nicholas Straussler. The Duplex Drive tanks form part of Major-General Hobart’s Funnies of the 79th Armoured Brigade, the family of specialised assault vehicles designed to support amphibious landings. The flotation screen allows a Sherman of more than thirty tonnes to float. The duplex-drive propellers push the tank forward in the water. Once the tank reaches shallow water or firm ground, the crew drop the screen. The tank then fights on land in the normal way.
The concept meets an urgent requirement identified in earlier operations. Infantry and engineers landing first on a hostile beach suffer heavy losses when no armour supports them. The Duplex Drive system makes it possible to put armoured firepower onto a defended shore at the same moment as the first waves. In some cases the tanks even arrive before the infantry.
Hobart then works to secure American support for his ideas. He arranges a visit by General Eisenhower and Field Marshal Brooke to Orford on 26 January 1944. They want to hear Hobart explain his methods and watch the equipment in action. Hobart briefs them on the tactics he develops for these new armoured roles. They examine training mock-ups of beach obstacles, minefields, ditches, walls, and pillboxes. The main event is a large demonstration of the division’s equipment. They watch Crab mine flails clear lanes. They observe lane-marking teams at work. They see the Bullshorn Plough, the ARK bridge, the Small Box Girder Bridge, the Wurlitzer, Snakes, Crocodiles, Duplex Drive tanks, and AVREs. They also watch a full combined-arms breach rehearsal. Eisenhower is particularly impressed. He returns convinced. He recommends to Bradley that the Americans adopt several of these British innovations for their own beach assaults.
The United States Army recognises the value of the Duplex Drive system during the planning for Normandy. In the Pacific theatre the United States Marine Corps employs amphibious tractors, known as Landing Vehicle Tracked Amtanks, fitted with light howitzers. These vehicles perform well in island assaults but lack the armour and endurance needed against the Atlantic Wall. The European theatre requires medium Shermans to accompany the first assault waves. Under British technical guidance, the United States equips selected tank battalions with Sherman Duplex Drive tanks in 1944. These units prepare for major amphibious operations in Europe.
Several independent American tank battalions are selected to receive amphibious training and Sherman Duplex Drive tanks in early 1944. These units include seasoned battalions that have fought in North Africa and Italy, and newer battalions raised for specialist roles. Their training in Britain takes place in strict secrecy. British instructors from the 79th Armoured Division oversee much of the work. Crews learn to handle the flotation screens and propellers. They also practise launches from landing craft in varied sea conditions.
The 70th Tank Battalion forms in 1940 as one of the first independent American tank battalions. It earns the nickname Landcrab. It lands with the 9th Division during Operation Torch in 1942 and fights through Tunisia. It also takes part in the Sicily campaign in 1943. After its arrival in England the battalion is attached to the 4th Infantry Division in March 1944 for the Normandy assault. In April 1944 Companies A and B receive their Sherman Duplex Drive tanks. Testing begins in March under tight security. The battalion trains at the Assault Training Center at Woolacombe in Devon and at hidden sites such as Torcross near Slapton Sands. By D-Day the battalion holds three medium companies. Companies A and B field Duplex Drive Shermans. Company C holds standard Shermans, including bulldozer tanks for obstacle clearance. A light tank company equipped with M5A1 Stuarts is also attached. Lieutenant Colonel John C. Welborn commands the 70th Tank Battalion in Normandy.
The 741st Tank Battalion is also selected for the amphibious role. It forms in 1942 and trains in the United States before deploying to Britain. In early 1944 it is chosen to support the 1st Infantry Division on D-Day. The battalion receives Duplex Drive Shermans and undertakes intensive amphibious training on the English coast with naval and engineer units. All three of its medium companies, A, B, and C, receive Duplex Drive tanks. The battalion has no combat experience before D-Day. Normandy becomes its first battle.
The 743rd Tank Battalion forms in 1942 and trains in desert and amphibious operations, including time at Camp Laguna in Arizona. It is later attached to the 29th Infantry Division for the Normandy landings. By D-Day the 743rd holds thirty-two Sherman Duplex Drive tanks divided across its companies. It also fields wading Shermans and bulldozer tanks. Lieutenant Colonel John Upham commands the battalion. His men land on Omaha Beach with the 29th Division.
The 191st Tank Battalion brings combat experience from Italy. It serves as a Fifth Army battalion often attached to the 45th Infantry Division during 1943 and 1944. It lands at Salerno and may take part in the Anzio fighting. For Operation Dragoon in August 1944 the battalion transfers to Seventh Army. It receives Duplex Drive Shermans for the southern France assault. Its companies practise naval landing techniques in the Mediterranean before the operation. During the Dragoon assault the battalion again supports the 45th Infantry Division on the beaches of the French Riviera.
The 753rd Tank Battalion also fights in Sicily and Italy. It possibly serves at Salerno. It is chosen to support the 36th Infantry Division, the Texas National Guard division, during Operation Dragoon. It receives a number of Duplex Drive tanks and trains in short-distance launches in the calmer Mediterranean waters. Its companies land with the 36th Infantry Division in August 1944.
The 756th Tank Battalion fights in Italy with the 3rd Infantry Division, including at Anzio and during the drive on Rome. For the Dragoon landings the battalion receives one company of Duplex Drive Shermans. This company holds eight tanks. The battalion trains in launching procedures from landing craft in the weeks before the assault.
The 736th Tank Battalion begins as a special unit equipped with top-secret Canal Defence Light tanks. These searchlight tanks are intended for night fighting. The battalion trains at Camp Bouse in Arizona during 1943. It deploys to England in April 1944 but does not take part in Normandy. It lands in France in August 1944 and in November becomes a standard tank battalion. Its Canal Defence Light equipment is never used in combat. The battalion spends late 1944 containing German pockets in Brittany, including positions near Lorient and Saint Nazaire. In early 1945 the battalion is chosen to receive Duplex Drive Shermans for the Rhine crossing. Company C trains on Duplex Drive tanks in early 1945. By March 1945 the battalion is attached to the 83rd Infantry Division and prepares to support the assault across the Rhine.
The 738th Tank Battalion follows a similar path. It also trains at Camp Bouse during 1943, probably with Canal Defence Light tanks or other specialist equipment. It later becomes a Mine Exploder tank battalion equipped with experimental devices for clearing minefields. By 1945 it is refitted as a conventional tank battalion. It becomes one of the units selected to field Duplex Drive tanks for river crossings. Alongside the 736th Tank Battalion it prepares to employ Duplex Drive Shermans during Operation Plunder, the Rhine assault of March 1945.
Each battalion undergoes extensive amphibious training. Crews swim their tanks in lakes and off British coasts. They practise embarking and launching from landing craft. They rehearse rapid removal of the flotation screen after landing. They are trained in escape procedures and receive Davis Submerged Escape Apparatus breathing equipment and inflatable life vests for emergencies. Training also focuses on preventing carbon monoxide build-up inside the canvas screens and dealing with bilge pump failures. By June 1944 the American Duplex Drive battalions reach the highest level of readiness possible for their first combat tests.
D-Day arrives on 6 June 1944. The American Duplex Drive tanks receive their harshest test during the landings on Utah and Omaha Beaches. The 70th Tank Battalion lands first on Utah Beach with the 4th Infantry Division. The plan calls for the battalion’s Duplex Drive Shermans to launch from their landing craft about one thousand yards offshore. They are expected to swim in just ahead of the first infantry at H-Hour. On the approach one landing craft carrying four Duplex Drive tanks is sunk by German artillery. Those four tanks are lost. The remaining twenty-eight Duplex Drive Shermans launch into comparatively calm water about nine hundred metres from the beach. Conditions favour them. Twenty-seven of the twenty-eight reach the shore safely.
The Duplex Drive tanks drift slightly off-course. A thick naval smoke screen hides landmarks. They come ashore nearly two thousand yards from their planned sector. The error proves unimportant. German resistance on Utah Beach is scattered and weak compared to Omaha. After landing, the companies of the 70th link with assault teams of the 8th Infantry Regiment. One platoon of Sherman tanks moves with the 3rd Battalion, 8th Infantry along Causeway Two. On the causeway they find an 88 mm gun covering the route and a large crater in the road. Two Shermans are lost during this advance, one to a mine and one to the 88. Another Sherman silences the enemy gun with a direct hit. When the causeways are open, the 4th Infantry Division advances inland rapidly. Utah Beach becomes the most successful of the American landings. The work of the 70th Tank Battalion, using both Duplex Drive Shermans and wading Shermans fitted with deep snorkels, helps secure the beachhead. The operation proves that the Duplex Drive concept works under favourable conditions.
Omaha Beach proves very different. Omaha becomes the most severe test for the Duplex Drive tanks. Two battalions take part. The 741st supports the 1st Infantry Division on the eastern sectors known as Easy Red and Fox. The 743rd supports the 29th Infantry Division on the western sectors known as Dog Green and Dog Yellow. Each battalion brings thirty-two Duplex Drive Shermans and additional wading or bulldozer Shermans. The assault plan requires the tanks to launch three to five thousand yards offshore. This long distance is intended to bring the tanks to the beach at the same moment as the infantry. The sea state, however, is far worse than predicted. The Channel heaves with waves between one and a half and nearly two metres high. The tanks are designed for calm seas with waves only about thirty centimetres high.
At about 05.40 the 741st Tank Battalion begins launching. Twenty-nine Duplex Drive tanks enter the water. Almost at once disaster unfolds. Twenty-seven sink before reaching the beach. Most go down within minutes as waves pour over the canvas screens. Later inquiry shows that many tanks must turn broadside to correct their drift, exposing their screens to swamping waves. Two crews with sailing experience manage to keep their tanks bow-on to the sea. These two Shermans miraculously reach Omaha Beach. Some crews transmit warnings, urging others not to launch at long range. The 743rd Tank Battalion on the western sectors takes note. Except for a few tanks forced off a sinking craft, the 743rd does not launch at sea. Most of its Shermans land directly by driving off their landing craft in the surf about ten minutes after H-Hour.
When the infantry of the 1st and 29th Divisions land on Omaha, most of the 741st’s sector has no tank support. Only two of the twenty-nine Duplex Drive tanks from the 741st reach the beach by swimming. A few more tanks, possibly from reserve platoons that do not launch, later arrive by landing craft. On the 29th Division’s front the 743rd delivers more tanks intact. Its Shermans drive off their landing craft in shallow water. Even so, Omaha receives only a fraction of the planned armour in the crucial opening hour. The absence of tanks contributes to the extremely high casualties among the first infantry waves. Troops are left exposed under heavy fire from bunkers and obstacles the tanks were intended to destroy.
By mid-morning some of the 743rd’s Shermans, including bulldozer tanks, and a handful of surviving tanks from the 741st manage to move up the tidal flat as the tide falls. They engage strongpoints and support the infantry at close range. By the afternoon more American armour arrives, including reserve tanks from the 745th Tank Battalion. German positions begin to collapse. The cost is heavy. Of the 112 tanks assigned to Omaha’s first wave, twenty-seven Duplex Drive tanks from the 741st sink at sea. Additional Duplex Drive and wading Shermans are knocked out by enemy fire or swamped near shore. At least five tank crewmen drown, though most are rescued by naval craft or reach land using life vests and belts.
The decision of the 743rd to land directly spares it similar losses. Nearly all its Duplex Drive tanks are delivered intact. Only one landing craft hit by artillery costs it four tanks. The 743rd later receives a Presidential Unit Citation for its performance. The 741st, despite its disaster offshore, fights with determination for the rest of the Normandy campaign. It is re-equipped and continues to support the 1st Infantry Division. The fate of the 741st becomes one of D-Day’s starkest warnings. The battalion’s losses underline the limits of the Duplex Drive system in heavy seas. Their experience, however, shapes later amphibious operations and likely prevents similar disasters elsewhere.
Operation Dragoon begins on 15 August 1944. The Duplex Drive tanks next see action in this assault on the French Riviera. Three American tank battalions deploy a total of thirty-six Duplex Drive Shermans. These are the 191st, the 753rd, and the 756th Tank Battalions. Each battalion supports a different American infantry division of Seventh Army. The lessons of Normandy shape every part of the plan. The Mediterranean is calm in August. The launch distances are shorter and carefully controlled.
The 756th Tank Battalion lands with the 3rd Infantry Division at Red Beach near Saint-Tropez. It launches eight Duplex Drive Shermans at about two thousand five hundred yards. Two are lost. One is swamped by the bow wave of a landing craft. Another strikes an underwater obstacle and sinks. The remaining six reach the shore and provide immediate fire support during the first minutes of the landing.
The 191st Tank Battalion supports the 45th Division at Alpha Beach. Its commanders choose a safer method. All twelve of the battalion’s Duplex Drive tanks are landed from their craft onto or very near the beach. They roll off in shallow water and begin firing at once. Several of these tanks hit mines shortly after landing. Five Duplex Drive tanks of Company C are immobilised. The event shows that a safe surf landing still carries serious risks.
The 753rd Tank Battalion supports the 36th Division at Camel Beach. It launches half of its Duplex Drive tanks at sea. Eight tanks swim ashore successfully. The remaining eight land directly later in the day. The operation as a whole shows how effective Duplex Drive tanks can be under proper conditions. Out of thirty-six Duplex Drive tanks used, only a few are lost. The presence of Sherman tanks from the first moments helps the American divisions overcome the light German coastal defences. Within hours the Allied beachheads in Provence are secure with relatively low casualties. The careful handling of the Duplex Drive force proves decisive and validates the adapted approach learned from Normandy.
In the final months of the war the Duplex Drive tanks gain a new purpose. They support Allied armies in the crossing of major rivers in north-west Europe. The largest of these operations is Operation Plunder, the assault across the Rhine on 23 and 24 March 1945. Two American battalions, the 736th and the 738th, receive Duplex Drive Shermans for this task. They operate alongside British Duplex Drive units. Together they support the XVIII Airborne Corps and other formations of the American Ninth Army during the crossing.
Company C of the 736th Tank Battalion, attached to the 83rd Infantry Division, launches its Duplex Drive Shermans into the Rhine under cover of darkness early on 24 March. The planners understand the strength of the current and adjust accordingly. Tanks enter the river upstream from their intended landing points. The current then carries them towards the correct zone. Earlier in the night, engineer units cross the river in Buffalo amphibious carriers. These carriers deliver and lay landing mats on the German bank to give the swimming tanks firm ground to climb onto.
The crossings prove highly successful. Some Duplex Drive tanks are lost in the Rhine. A few are swamped or swept away. Most, however, reach the far shore and strengthen the bridgeheads at once. The 738th Tank Battalion, attached to the 79th Infantry Division, also puts Duplex Drive Shermans across near Wesel. The British 79th Armoured Division’s Duplex Drive regiment, the 44th Royal Tank Regiment, works with the American battalions throughout the assault. Their combined effort places tanks on the German bank before the engineers complete the heavy pontoon bridges. Allied commanders judge the Duplex Drive tanks vital to the Rhine crossing. The operation becomes a striking example of tanks acting as amphibious cavalry while under fire.
A final use of Duplex Drive Shermans occurs on 29 April 1945. British troops of the Staffordshire Yeomanry swim several tanks across the Elbe in Germany. The American Army does not use Duplex Drive tanks on the Elbe. The war is near its end, and further assault crossings are no longer required.