World War Photos

Sherman DD and M4A1 Omaha Beach 6 June 1944

The Duplex Drive (DD) amphibious tank, closely associated with Operation Overlord, played a crucial role in the D-Day landings. Designed by Hungarian-born engineer Nicholas Straussler, the DD tank was an innovative solution to the challenge of amphibious warfare, allowing standard tanks to be modified for water crossings. The development of the DD tank involved several stages, key milestones, and collaborative efforts between the British and American forces.

Development of the DD Tank

1. Early Concepts and Prototypes:

   • Nicholas Straussler initially proposed the idea of using a collapsible canvas skirt around a standard tank to provide buoyancy. The first application of this concept was to a Tetrarch light tank in 1941, but the prototype had too little freeboard and was prone to sinking.
   • The British Tank Board approved a more refined design in September 1941, which was based on the Valentine infantry tank. This design included higher screens, rigid supports, and a propeller screw powered by the tank’s engine, enabling it to move through water.

2. Valentine DD Tank:

   • The Valentine DD tank became the first practical version of this concept. Production approval was granted in July 1942, with production starting in March 1943. However, the Valentine DD tank, while effective, had limitations in speed and seaworthiness.

3. Sherman DD Tank:

   • Recognizing the limitations of the Valentine DD, the Royal Armoured Corps (RAC) supported the development of a Sherman DD tank in 1943. The British General Staff approved the conversion of 500 Shermans for Operation Overlord, later increasing the requirement to 900.
   • The British Ministry of Supply tried to involve the US government in the project, but the US Army initially showed little interest due to past experiences with amphibious tank prototypes like the M3E4. However, the urgency of Operation Neptune eventually led to the US agreeing to manufacture DD tanks.

4. US Involvement and Production:

   • In October 1943, the US Army’s European Theater of Operations (ETOUSA) requested 199 Sherman DD tanks for the upcoming operation. Production was expedited due to the support of high-ranking officers, including Lt. Gen. Jacob Devers and Gen. George Marshall.
   • The first ten American-assembled DD tanks arrived in the UK by March 10, 1944, a rapid turnaround given the tight timeline.

5. Challenges and Adjustments:

   • The British faced delays in converting their Shermans, leading to a shortage of DD tanks by the planned invasion date. As a result, they requested additional tanks from the US, which increased their own production to meet both American and British needs.
   • By May 1944, the British had converted fewer tanks than expected, so Valentine DD tanks were used to supplement the regiments.

Role in Operation Overlord

The DD tanks were crucial during the D-Day landings on June 6, 1944. These tanks were intended to lead the assault by crossing the English Channel under their own power and then driving onto the beaches, providing immediate armored support for the infantry. While some tanks were successful, others faced difficulties due to rough seas, which led to losses before they could reach the shore. Despite these challenges, the DD tanks that made it to the beaches played a significant role in the success of the landings.

The Duplex Drive tanks, particularly the Sherman DD, represent a remarkable feat of wartime innovation and international collaboration. Their development was a direct response to the unique challenges of amphibious warfare, and despite the technical and logistical challenges, they became a symbol of the ingenuity and determination that characterized the Allied efforts in Operation Overlord.