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Caterpillar D7 Bulldozer

The Caterpillar D7 series medium bulldozer began service with the U.S. military during World War II. With upgrades and changes, it has been a workhorse for the U.S. Military for over fifty years, fulfilling its primary earthmoving role as well as a host of other roles discovered for it, for example mine clearing with a special flail adapter kit. Although very versatile, the ability of the D7 to operate varies with soil conditions.

For the Army, the D7 dozer is the primary earthmover for construction of survivability positions and antitank ditches. It must be transported by trailer due to its poor mobility. Three dozers are assigned to corps combat engineer companies and CONUS divisional combat engineer companies. The other U.S. Military services have roles for the D7 in their operations around the world.

USMC D7 Bulldozer
USMC D7 Bulldozer.

Today in WW II: 25 Oct 1943 American and New Zealand troops land at Mono and Stirling, Treasury Islands, south of Bougainville [25-27 Oct].  More 
25 Oct 1944 First operation by the Japanese Kamikaze Special Attack Force: 55 kamikazes strike 7 carriers and 40 other ships, sinking six, off Leyte, Philippines.
25 Oct 1944 Battle off Samar [Leyte]: US Admiral Sprague skillfully prevents a loss to the stronger Japanese force under Japanese Admiral Kurita.
25 Oct 1944 Battle off Cape Engaño (Leyte): lopsided naval battle resulting in the loss of most of Japanese Northern Force to US Admiral Halsey's carrier planes and battleships [25-26 Oct].
25 Oct 1944 Soviet Red Army enters Kirkenes, the first town in Norway to be liberated from the Germans.
Visit the Olive-Drab.com World War II Timeline for day-by-day events 1939-1945! See also WW2 Books.

Models of the Caterpillar D7 Bulldozer

Heavy Tractor, M1 Caterpillar D7 from TM 9-1773, Figure 1 (September 1943)
Heavy Tractor, M1 Caterpillar D7 from TM 9-1773, Figure 1 (September 1943).

The Cat D7 bulldozer has had a long service life in the U.S. military, including these models:

  • D7 7M series, manufactured 1940-1944, approx 10,000 produced. D8800 engine, 74 inch track gauge
  • D7A 1T1001 series, manufactured 1943, 138 produced. Armor plated 7M with twin hydraulic cylinders, rear mounted Hyster D7N winch
  • D7 3T series, manufactured 1944-1955, over 28,000 produced
  • D7 4T series, manufactured 1944-1945
  • D7 6T series, manufactured 1945
  • D7C, manufactured 1955-1959. D339 diesel engine, hydraulic track adjusters
  • D7D, manufactured starting 1959. Oil-cooled brakes, steering clutches
  • D7E. Procured 1965-67, NSN 2410-01-050-9628 with ROPS
  • D7F Tractor, Full-Tracked, Low-Speed DED (diesel engine driven), Medium Drawbar Pull. Procured 1971, with ROPS NSN 2410-00-185-9792. Service life extension program in mid-1990s to make compatible with D7G.
  • D7G Tractor, Medium, Full-Tracked. Procured 1970s. Diesel engine powered, track-type hydraulic bulldozer equipped with a blade and modular cab incorporating a Rollover Protection Structure (ROPS). The D7G may also be equipped with a Winch, Ripper or Drawbar. As used by USMC NSN 2410-01-155-1588.
  • D7H Tractor, Full Tracked, Low Speed. NSN 2410-01-423-0931 with winch and cab
  • D7R Tractor, Full Tracked, Low Speed. Power shift. NSN 2410-01-451-4048

The NSNs stated for the D7 models are typical, but many other NSNs were assigned for use by the U.S. service branches depending on optional equipment and other factors.

During WW II, the D7 was one of the bulldozers collectively known as "Tractor, Heavy, M1." The Caterpillar D7 models were Ordnance G-126. Equivalent tractors were produced during WW II by Allis-Chalmers Co. (Model HD10W, G-98) and International Harvester Co. (Model TD18, G-101). About one thousand Caterpillar D7s were also produced by American Car & Foundry under license when WW II military orders exceeded Caterpillar's capacity.

Caterpillar Tractor Co. produced the D7 until Caterpillar's military business was reorganized into Caterpillar Defense & Federal Products (Mossville, IL).

Caterpillar Model D7R Dozer

After more than 60 years, in the mid-2000s, the Caterpillar D7R became the latest D7 model to be modified for military use. The D7R is equipped with an elevated sprocket undercarriage for added durability and efficiency during earthmoving. The operator's station provides excellent observation of the blade and the rear of the machine for maximum operator productivity. Equipped with differential steer, its dual twist tiller provides for excellent maneuverability and one-handed, finger-tip directional, gear range, and steering controls with less operator fatigue. Interior noise levels are reduced to 83 dB, a level that does not require ear protection. Operational weight of the D7R dozer is 59,000 lbs. Military modifications include transport provisions, blackout lights and CARC paint.

Caterpillar D7 Dozer Characteristics

Weight50,000 lbs
Width144 inches
Length273 inches
Height132 inches
Engine200hp Cat 3306T diesel
Speed: Forward6 mph
Speed: Reverse7.1 mph
Fuel Tank120 gals
Fuel Consumption6 gal/hr

Note: The tabulated characteristics are based on the D7G model.

Manuals for the Caterpillar D7 include TM 9-1773 Heavy Tractor, M1 Caterpillar D7 Ordnance Maintenance (September 1943) and parts list SNL G-126. Modern manuals for the Tractor, Full Tracked, Low Speed DED are in the series TM 5-2410-237-xx depending on maintenance level.

Find additional photos and hi-res versions of the Caterpillar D7 Bulldozer at the Olive-Drab Military Mashup:

829th Engineer Construction Company MSGT Knowles Freeman, Pensacola, FL, atop a Caterpillar D7 bulldozer while building an airport near Eye, England, 2 Mar 1943.
D7 bulldozer in front of the Marine Corps Engineer School, Courthouse  Bay, Camp Lejeune, NC.
1989 Caterpillar, full tracked, low speed, diesel engine driven bulldozer, model D7G, 78 in gage MED, draw bar pull, s/n 3GF00236, with Caterpillar 57 winch, with CAT 3306B diesel engine, direct injected, transmission# 2GA06855, with air conditioning, hour meter reads 2083, 22" track and 7S dozer blade. Courtesy: Government Liquidation LLC.
An engineer uses a D7 bulldozer to repair a road damaged by retreating enemytroops, Korea, 1950.
US Army Combat Engineers with D7 bulldozer clear a road, WWII.  A WC-54 3/4-ton ambulance is in the background.
A D-7 bulldozer strips and does rough grading on a forward airstrip designed to accommodate reconnaissance, supply, and evacuation aircraft, Korea, 1950s.

Recommended Books about the Caterpillar D7 Bulldozer

Caterpillar D7 7M series tractor, operated by MSGT Knowles Freeman from Pensacola, FL, 829th Engineer Construction Company, while building an airport near Eye, England, 2 March 1943.  Although not on this unit, the D7 7M tractors were typically fitted with a  LeTourneau WCK-7 angledozer blade operated by the rear mounted power control unit
Caterpillar D7 7M series tractor, operated by MSGT Knowles Freeman from Pensacola, FL, 829th Engineer Construction Company, while building an airport near Eye, England, 2 March 1943. Although not on this unit, the D7 7M tractors were typically fitted with a LeTourneau WCK-7 angledozer blade operated by the rear mounted power control unit.

D7A armored bulldozer, 1 May 1944
D7A armored bulldozer, 1 May 1944.

D-7 bulldozer working a borrow pit, Vietnam, 1960s
D-7 bulldozer working a borrow pit, Vietnam, 1960s.

USMC D7 Bulldozer photographed in Bosnia
USMC D7 Bulldozer photographed in Bosnia.

USMC D-7 Countermine Bulldozer
USMC D-7 Countermine Bulldozer.

D7 Bulldozer, Naval Beach Group 1
D7 Bulldozer, Naval Beach Group 1.

D7 Bulldozers, Camp Liberty, Iraq, April 2005.  Operators are Spc. Dwayne Sinegal and Spc. Chris Johnson with A Company, 1088th Engineer Bn., 256 Brigade Combat Team
D7 Bulldozers, Camp Liberty, Iraq, April 2005. Operators are Spc. Dwayne Sinegal and Spc. Chris Johnson with A Company, 1088th Engineer Bn., 256 Brigade Combat Team.

D7F with 7S bulldozer blade (FSN 2410-177-7284 or NSN 2410-00-177-7284) at the Texas Military Forces Museum, Camp Mabry, TX, 30 January 2006.  Photo:  Courtesy of Bob Pettit
D7F with 7S bulldozer blade (FSN 2410-177-7284 or NSN 2410-00-177-7284) at the Texas Military Forces Museum, Camp Mabry, TX, 30 January 2006. Photo: Courtesy of Bob Pettit.

D7F with 7S bulldozer blade (FSN 2410-177-7284 or NSN 2410-00-177-7284) at the Texas Military Forces Museum, Camp Mabry, TX, 30 January 2006.  Photo:  Courtesy of Bob Pettit
D7F with 7S bulldozer blade (FSN 2410-177-7284 or NSN 2410-00-177-7284) at the Texas Military Forces Museum, Camp Mabry, TX, 30 January 2006. Photo: Courtesy of Bob Pettit.

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