Today in WW II: 12 Jul 1943 Tank battle at Prokhorovka, during the Battle of Kursk, greatest tank battle of WW II, unsurpassed until Operation Desert Storm in 1992.
Development of the M4 Sherman Bulldozer Tank in World War II
Bulldozer M1A1 mounted on Sherman medium tank M4A3 with horizontal suspension. From TM 9-719 Tank Mounting Bulldozer M1 and M1A1 (August 1948).
The association of a bulldozer blade with a medium tank was first tried by the British Army in North Africa during their campaign of 1940-1941, as a means of eliminating mines in the path of advance. By 1942, mine detectors were capable of finding hidden mines and the bulldozer blade equipped tank could then excavate the mines and move them to the side. This could be accomplished without significant risk to the tank crew who were protected by the tank's armor and had the tank's guns for defense.
After American officers observed the British success, the US Army Corps of Engineers was assigned the role of creating and testing a tank/bulldozer vehicle. During 1942, the Engineer Board considered several different ideas. Destroying mines was only one potential task for a tank dozer that could also tackle overcoming ditches, craters, and other antitank obstacles. It was not obvious that a tank was best; armored tractors were considered as an alternative design.
Ignoring bureaucratic struggles between Ordnance and Engineers, and conflicting orders from Services of Supply, Major Karl F. Eklund, who supervised the Mechanical
Equipment Section at the Engineer Board, pushed ahead with the tank dozer development. Working with the Caterpillar Tractor Company and two industrial producers of tractor blades -- the LeTourneau and LaPlante-Choate Companies -- Eklund and the board's project engineer, William J. Murwin, experimented with mounting various blades on tanks. The board's researchers concentrated on developing the best possible blade for mine removal. Further, they felt that a blade capable of removing mines might also be useful in other clearing operations. Eklund talked each company into constructing two pilot models, each with a different style blade, at no expense to the US government. The board and the companies tried several variations of weight, height, teeth, hydraulic and cable controls, designs to control the blade's rising out of the ground, and other features. The project's high standards required that the tank dozer be as easy to control as a bulldozer.
Eklund conducted experiments at Fort Pierce, Florida's beach obstacle course; at Fort Knox, Kentucky, with the armored forces; and at other installations. The June 1943 Fort Pierce tests of the LeTourneau and LaPlante-Choate blades were successful, making the tank dozer was a reality. Meanwhile, Ordnance researchers continued experimentation on a blade suitable for light tanks to use in the Pacific's jungle warfare.
Both tank dozer blades were then approved and purchased for the Army's M4 Sherman medium tanks as what was officially named the "Bulldozer, Tank Mounting for M4A1, M4A2,
M4A3 Tanks." The LeTourneau blade was cable operated and the LaPlante-Choate system used a hydraulically-operated blade. By September 1943 all levels of the Army accepted
the usefulness of the new blades, which operated from the tank's internal power supply and which the driver could jettison within ten seconds in case of emergency. Large-scale production of the dozer package began in December 1943 and the first units arrived in Italy in time for the spring 1944 Allied offensive.
While efforts to produce a standard tank mounted bulldozer were in process, field modifications under local command were already in use. By 1943 the hydraulic dozer blade from a Caterpillar D8 had been fitted to an M4 Sherman as well as other combinations of tank and blade.
The standardized version of the bulldozer attachment for the M4 Sherman was finalized with two variants, the M1 for vertical suspension tanks (VVSS) and the M1A1 for the wider horizontal suspension (HVSS). The M1A1 blade is 14 inches wider than the M1 and the M1A1 has a 3-section telescopic jack while the M1 has a single section telescopic jack.
Manuals produced for the Bulldozer, Tank Mounting include:
TB ENG 9 Bulldozer, Tank Mounting For M4A1, M4A2, M4A3 Tanks (1 March 1944)
TB ENG 41 Bulldozer, Tank Mounting, For M4A2 and M4A3 Tanks, 1944 Series (20 September 1944)
TM 9-719 Tank Mounting Bulldozer M1 and M1A1 (August 1948)
Use of the M4 Sherman Bulldozer Tank in World War II
Italy was the first combat use of the Sherman Bulldozer tanks. There the German Army was careful to destroy the bridges, culverts, and mountainside shelf roads that the Allies needed in their advance up the Italian peninsula. German units then used light-caliber weapons to stop the men and bulldozers sent forward to restore the roads. The Sherman tank-dozers solved this problem making immediate positive changes in the situation. At the Anzio beachhead, tank-dozers were used to extinguish fires in the large ammunition dumps that were targeted by German artillery. Once the tank-dozers were available, even large fires could be quickly contained by scooping dirt and pushing it over the burning containers.
The lessons learned in Italy made the Sherman-dozer an item of high demand for the European Theater (ETO) from the invasion of Normandy to V-E Day. General Eisenhower expressed a personal interest in increasing the supply of these versatile machines, but manufacturing never caught up with orders from the field. For D-Day, a total of 393 tank dozers were requisitioned prior to 9 May 1944 for US forces, and another 100 for the British and 24 for the French. Only 24 were received in April 1944 and another 81 in May, far fewer than the requests. Nonetheless, the tank dozers were essential in clearing beach obstacles and allowing units to move off the beaches on D-Day and immediately after. Following D-Day in the early stages of the Battle of Normandy before the Culin Cutter was developed (also called Rhino or Hedgerow Buster), the dozer Sherman was the best method of breaking through the Bocage hedgerows. Working with artillery and infantry, the tank dozers were highly effective in disrupting German defenses and making territorial gains. As the Allied armies moved out of France and closer to Germany, the tank dozers prepared tank and gun emplacements, cleared roadblocks, removed wrecked vehicles, snow and debris, filled craters, cleared mines, and built approaches for river crossings. While there were some mechanical and operational problems with the Sherman tank dozer, the value far outweighed the deficiencies with great benefit to the users.
Relatively few Sherman tank bulldozers were used in the Pacific Theater of WW II, with some dozer-equipped light tanks filling the role. Where the Shermans were used, the tasks were similar to the ETO, such as clearing beach obstacles, creating ramps for landing craft, filling craters, removing road obstacles, sealing cave defenses, and general earthmoving duties.