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The armored bulldozer is a basic tool of combat engineering. These combat engineering vehicles combine the earth moving capabilities of the bulldozer with armor which protects the vehicle and its operator in or near combat. Most are civilian bulldozers modified by addition of vehicle armor/military equipment, but some are tanks stripped of armament and fitted with a dozer blade. Some tanks have bulldozer blades while retaining their armament, but this does not make them armored bulldozers as such, because combat remains the primary role — earth moving is a secondary task.
World War 2 
The first armored bulldozer was developed by the British during World War 2. This was a conventional Caterpillar D8 bulldozer fitted with armor to protect the driver and the engine. The work was carried out by Jack Olding & Company Ltd of Hatfield. The bulldozer was one of several strange armored vehicles that were collectively referred to as "Hobart's Funnies" and were operated by the British 79th Armoured Division in support of armored assaults.
The bulldozers were produced in preparation for the Battle of Normandy with the tasks of clearing the invasion beaches of obstacles and quickly making roads accessible by clearing rubble and filling in bomb craters.
As allied armies advanced through Europe, the armored bulldozer was found to be too slow—there was a need for well-armored, obstacle clearing vehicle that was fast enough to keep up with tank formations. This need was met by the Centaur Bulldozer—a Centaur tank with the turret removed and a bulldozer blade fitted. Centaur bulldozers were still in use with the British Army at the time of the Korean War.
Modern usage 
Caterpillar does not manufacture a military version of the D9 and D7 per se, but the attributes that make the D9 popular for major construction projects make it desirable for military applications as well. It has been particularly effective for the Israel Defense Forces (IDF) and for the United States armed forces (the Marine Corps and the US Army) in Iraq.
Israeli usage 
The Israeli Armored D9 — nicknamed Doobi (Hebrew: דובי; lit. teddy bear) — is a Caterpillar D9 bulldozer that was modified by the Israel Defense Forces, Israeli Military Industries and Israel Aerospace Industries to increase the survivability of the dozer in hostile environments and enable it to withstand heavy attacks.
The D9R, the latest generation of D9 bulldozers in IDF service, has a power of 405 to 410 horsepower (302 to 310 kW) and drawbar pull of 71.6 tonnes-force (702 kN). It has a crew of two, an operator and a commander. It is operated by the TZAMA (צמ"ה = ציוד מכני הנדסי, Mechanical Engineering Equipment) units of the Israeli Engineering Corps.
The main IDF modification is the installation of an Israeli-made armor kit which provides armor protection to the mechanical systems and to the operator cabin. The operator and commander are protected inside an armored cabin ("the cockpit"), with bulletproof windows to protect against bombs, machinegun, and sniper fire. The IDF also developed a slat armor add-on to deflect RPG rounds. The fitted armor package adds roughly 15 additional tons to the production-line weight of the D9. The modified D9 bulldozers can be fitted with disparate features, such as crew-operated machine guns, smoke projectors, or grenade launchers.
The IDF uses the D9 for a wide variety of engineering tasks, most notably home & structure demolition, even if under fire, as well as earthworks, digging moats, mounting sand barriers, building fortifications, rescuing stuck, overturned or damaged armored fighting vehicles (along with M88 Recovery Vehicle), clearing landmines, detonating IEDs and explosives, clearing terrain obstacles and opening routes for armored fighting vehicles and infantry.
During the Second Intifada the armored D9 bulldozer gained notoriety as being an effective tool against Palestinian fighters & civilians, as they were almost impervious to Palestinian weapons and withstood even RPGs and belly charges with more than 100 kg and even half a ton of explosive. Therefore they were used to open safe routes for IDF forces and detonate explosive charges. The bulldozer was used extensively to clear shrubbery and structures which could be used as cover. In addition they razed houses of civilians and the families of suicide bombers.
Following several incidents where armed Palestinians barricaded themselves inside houses and killed soldiers attempting to breach the entries, the IDF developed "Noal Sir Lachatz" (נוהל סיר לחץ "Pressure Pot Regulation") in which D9s and other engineering vehicles were used to bring them out by razing the houses; most of them surrendered because of fears of being buried alive.
While Palestinians saw the D9 as a devastating weapon, and human rights groups criticized it for the massive damage it caused to Palestinian infrastructure, Israelis and military experts claimed the D9 was a necessary tool for combatting insurgency and a key factor in reducing IDF casualties.
United States usage 
During the first Gulf war the USA purchased tractor protection kits (TPK) from the Israel Military Industries (IMI) for their Caterpillar D7 bulldozers. The armored bulldozers were mainly used in mine clearing applications. During the preparation to the war in Iraq in 2003 the United States Army purchased several D9 armor kits from the IDF and used them to produce similarly fortified D9s. These have been used to clear destroyed vehicles from roads, dig moats, erect earthen-barriers, and construct field fortifications. D9s have also been used to raze houses which sheltered insurgent snipers. Military reports on the Conflict in Iraq say that the D9s were found very effective and "received highly favorable reviews from all that benefited from their use".
See also 
- Al-Aqsa Intifada
- Bob Semple tank - Improvised tanks constructed from bulldozers.
- Combat engineering vehicle
- Demining - used for landmines clearance
- Engineering vehicles
- Israeli Engineering Corps
- Marvin Heemeyer - Constructed a home-made armored bulldozer dubbed 'Killdozer' and went on a rampage.
Notes and references 
- Field Report: United States Marine Corps Systems Command Liaison Team, Central Iraq, 20 April to 25 April 2003.
- Army's new D9 bulldozer digs into duty in Kuwait - The US army tests the armored D9R for the Iraqi campaign