The T18 "Boarhound" emerged from a two-part United States Army Ordnance requirement which sought both a medium- and heavy-class armored car design for service in World War 2 (1939-1945). The specifications were revealed in July of 1941. To fulfill the medium-class armored car request, Ford Motor Company put forth its T17 (6x6 wheeled) and T17E1 (4x4 wheeled) models and these went on to become the "Deerhound" and "Staghound" cars respectively - about 4,000 were produced and saw widespread service with many countries including Britain - though neither served with the United States military. Work on the heavy-class armored car ultimately produced the T18 Boarhound which only served with the British Army during World War 2.
The Yellow Coach Company headed development of theT18 and a pilot vehicle was made available as soon as 1942. By now, the British had been at war for several long years and, now with the United States in tow, control of North Africa was of the utmost importance before the march on Rome and Berlin could be had. Armored cars were increasingly important in the desert terrain where their speed and maneuverability could be put to good use. A heavy armored car with medium tank qualities (armament, armor) seem to fit the bill for the British Army going forward.
The resulting T18 was a large armored car vehicle. It featured an 8x8 wheeled configuration in which two axles were paired at front and the remaining two paired at rear. Steering was through the front four wheels. The typical operating crew numbered five. The vehicle weighed in the 30-ton range and sported a running length of 20.4 feet, a width of 10 feet, and a height of 8.5 feet. A turret was sat over the hull superstructure at midships and initially armed with the American 37mm M6 anti-tank gun. A coaxial .30 caliber Browning M1919A4 air-cooled machine gun was the standard anti-infantry installation while a second M1919 was added to a ball mounting at the front-right hull. The driver was seated at front left. Armor protection for a vehicle of this type was rather good, ranging from 9.5mm to 50.8mm along the particular facings (more critical facings receiving greater armor thickness). Power was served through 2 x GMC 6-cylinder engines of 125 horsepower each (250 horsepower combined output) which allowed for road speeds to reach a useful 50 miles per hour and operational ranges out to 250 miles. Suspension was across all wheels for improved cross-country travel support.
Before the T18 was delivered to British Army units, it was already witnessed in the desert campaign that the American 37mm anti-tank gun was of limited value against the mid-generation German Panzers and heavier Italian tanks. As such there was a move to arm the new armored car with the American 57mm M1 anti-tank gun - these nothing more than locally-produced versions of the British QF 6-pounder series. With that change, the T18 became the modified "T18E2" (note the "T" developmental designation still in use) to which, upon acceptance into the British Army inventory, the vehicle was named "Boarhound". A six-wheeled variant was also in the works as the "T18E1" but its development was eventually cancelled before the product was realized. The 57mm main gun was afforded a stock of 60 x 57mm projectiles while 2,500 x 0.30 caliber ammunition was carried aboard.
The British intended to procure an impressive 2,500 of the type before priorities shifted. The T18E2 also showcased limitations in its design through few Boarhounds that actually made it into service. The vehicle was noted for its poor cross-country service despite its four-wheeled approach, dual engine layout, and suspension system. The design was also much too expensive to procure in number when compared to competing designs of the period which left total manufacture of Boarhounds at a staggeringly low 30 units by the end of its run. The few that did see service were used in a variety of roles where needed - from convoy protection and base defense to reconnaissance sorties and infantry support. Very few are thought to have seen actual combat.