When Crawlers Were Conquerors in World War II

Editor’s Note: This is the fourth in a series of articles on the contributions farmers and tractor manufacturers made to winning World Wars I and II. This article originally appeared in Ageless Iron Almanac.

Engage in a discussion regarding World War II armaments, and bombers, tanks, and battleships often dominate the conversation.

Yet, the lowly crawler was so important to war efforts that Fleet Admiral William “Bull” Halsey stated the four machines that were essential to winning the Pacific war were the submarine, radar, the airplane, and the bulldozer.

In fact, the term bulldozer was coined during the war to describe crawlers equipped with dozer blades.

Manufacturing crawlers for the civilian market were greatly diminished with the onset of World War II to slake the thirst of the military for the tractor.

Crawlers went to battle around the world transporting artillery and supplies, constructing fortifications, clearing jungles, and creating roads and airfields. They were particularly prized by the Marine Corps and the Navy’s Construction Battalion (Seabees) in the Pacific theater.

Crawlers were produced in great variety – from small, air transportable units that flew with airborne engineers to hulking brutes used to move the heaviest field artillery under adverse conditions.

Remade for Military Use

At the time, the War Department standardized crawlers into three categories.

Light-duty crawler tractors included Caterpillar model D4 an IHC model TD9.

Medium-duty crawlers (designated as M1 Medium) included Allis-Chalmers HD7W, Caterpillar D6, Cletrac HG, and IHC TD14.

M1 Heavy crawlers included Allis-Chalmers HD10W, Caterpillar D7 and D8, and IHC TD18.

Other crawler makes and models were procured during the war, but these three were the most commonly used.

Competitor Cooperation

The war effort also inspired competitors to join forces to meet the need. A great example of this was Caterpillar and LeTourneau. When the two companies teamed up, Cat provided crawlers and LeTourneau built dozer blades and scrapers by the thousands.

It’s estimated that just short of 10,000 Cat D7s alone, most bearing LeTourneau dozer blades, were built for the military between 1940 and 1944.

Bulldozers were often the first on the scene after the Marines secured a beach head on South Pacific islands. Thousands of Cat crawlers working with LeTourneau blades or scrapers pushed the Alaska highway through 1,400 miles of wilderness in two summers in response to Japanese landings on two Aleutian islands.

Unique Innovations

While the vast majority of crawlers put to war work consisted of modified variations of existing models, there were unique variation engineered for specific conditions. A prime example was the Clarkair model CA-1.

Designed by Clark Equipment Company, the CA-1 Airborne dozer was lithe in size, allowing it to be readily loaded onto cargo planes or even gliders, and then flown to forward war zones for use by the Army primarily for creating landing strips.

This baby crawler, complete with a hydraulically operated dozer blade, was powered by a Waukesha model FC151R gas engine. Clark developed the prototype.

The crawler would be built by Clark as well as Cleveland Tractor (Cletrac) and American Machinery and Metal. All told, some 1,100 CA-1 Airborne dozers were built.

The CA-1 would prove its worth when flown in by gliders at night behind the Japanese line in northern Burma.

Within 24 hours, airborne engineers using the little crawler prepared a 5,000-foot-long landing strip to accommodate additional gliders and C-47 transport planes, which brought in more men and supplies to secure a position for the Allies.