The original Australian mechanised unit was the Australian 1stLight Car Patrol, consisting of Ford cars each armed with a Vickers machine-gun which took part in operations in the Western Desert against the Senssui revolt of 1917 then in Palestine where it worked with the Australian Light Horse units until the end of the first Great War of the 20th Century. The Australian Army had been interested in mechanical warfare, but like the British interest was intermittent. In 1928 approval was given for the purchase of the first tanks in Australia, five Vickers Mediums with a turret and machine-gun.
     In 1929 a cadre of tank-trained officers and men was raised, the First Australian Tank Section was formed at Randwick in the State of New South Wales and the Second Australian Tank Section was raised in the State of Victoria. An armoured car unit had been formed in 1933 using the 19thLight Horse Regiment as the nucleus for cadres. After the outbreak of a second World War in Europe the recruiting for the four Australian Imperial Force (AIF) divisions for overseas service commenced. Australian Light Horse Regiments also contributed many trained personnel to the divisional cavalry regiments and to other armoured and motor units of the Royal Australian Armoured Corps. These Australian cavalry (reconnaissance) regiments fought in North Africa and the Middle East with a variety of vehicles ranging from Bren machine-gun armed carriers, or an anti-tank rifle, and Vickers light tanks to British cruiser Crusaders, American Stuart / Honey Lend-Lease light tanks, captured Italian M13/40's and French R35’s.
     During October 1939 Lieut-General Squires, an Englishman, Chief of General Staff, Australian Military Forces (AMF) had directed his procurement staff to investigate into local production facilities in manufacturing tanks. The Australian defence industry, at the time, had been tooled in the manufacture of Bren-carriers, the 2pdr (40mm) anti-tank gun carrier, and 3inch-mortar carrier, the scout car and light armoured car. They were the simplest types of Armoured Fighting Vehicle (AFV) to produce and manufacture in Australia, which were derivatives of the British machine-gun carrier Mk1 and the indigenous motor car industry and spare parts. These types of AFV’s did not represent suitable aggressive battlefield survivability but were available in large production numbers. Squires was guided by the threat of Japanese AFV’s and concluded that a light cruiser tank of 20-25mm armour, with a 2pdr gun and a crew of four, with wireless, 30mph maximum speed with good acceleration across country and a range of 150miles would at least match, or better the types of tanks that the Japanese could land in Australia. The Japanese had heavier tanks with bigger guns and thicker armour yet could not be off loaded from Japanese ships unless at a major port.
     Shortly afterwards Squires died, and his idea for a locally produced tank, until the shock in regard to blitzkrieg defeats of Poland in September 1939, then through Belgium in May and to France in June 1940. The build up of armoured forces in Australia began in December 1940 with the opening of the AFV School at Balcombe, then moving to Puckapunyal in the State of Victoria by February 1941. The most complex piece of machinery required by the Australian Army for the growth of these new all-armoured formations was undergoing enormous change in design throughout the Western Alliance. The project for an Australian made tank was also exacerbated by the Army attempting to lay the specifications on the design perimeters on a turret type tank capable of fighting German AFV’s. This may have had relevance in 1940, for the prospect of an AIF armoured force in North Africa seemed inevitable but the real enemy was to be Imperial Japan. Armoured training units were also formed and in July 1941 the raising of the 1st Armoured Division commenced. The intention was that this division would embark for the Middle East in February / March 1942, but this deployment did not take place due to the Japanese military thrust into the Mandated Territories of Australia.
     Beforehand the Australian Army with a fixation of fighting German main battle tanks continued to modify its development design which created chaos for the production authorities and eventually the Australian government gave design, development and manufacturing for AFV’s to the Department of Munitions and Supply. Although the Army still had enormous influence in design, was still requiring the highest standards in AFV procurement and imposed standards of performance in the design greatly exceeded Japanese tank capabilities. By the end of 1940 the hull was increased to 50mm and speed raised to 35mph. In February 1941 the turret armour had been increased to 75mm and hull armour raised to 65mm. These changes prevented rudimentary preparations for tank production, then stability in development and design of the Australian Cruiser Mark 1 (ACMk1) tank was finally achieved by the effort of Colonel W.D.Watson, a British tank design expert. Since December 1940 he had tried to combine the best features of British tank design with United States of America (US) automotive science to produce a tank that could rival German panzers. No tank engines were available, and as a stopgap three Cadillac V8 motors were stuck together in a triple layout with the combined power transmitted by a single shaft from the transfer box to the main clutch and gearbox. They were mounted radially on a steel frame arranged around a common crankcase and credit for much of this work goes to Mr. R. Perrier, a French tank designer who’d been in Japan and made his way to Australia during the year.
     The US M3 medium tank synchromesh gearbox was redesigned to suit the gear cutting machinery in Australia so it became a crash gearbox. Other parts for the power unit transfer box, drive train and transmission were also modified from available US M3 tank parts for Australian manufacturing and the suspension being based on the unfavourable M3 design, but an Australian all-steel track was produced and fitted. The plate armour was too thick to be rolled in Australia but the steel manufacturing industry succeeded in finding a formula for suitable armour casting using indigenous alloys which increased the armour ballistic qualities of the full cast hull and separate cast turret. The Australian cruiser tank, or Sentinel with its cast hull, for a tank of this size, had preceded the American M48 by ten years and was acknowledged as a real contribution, at the time. As more British and US built tanks arrived in June 1942 General Blamey, the C-in-C of the Australian Army forces, explained that overseas tanks were obsolete and Australia would have to produce its own tank if supply lines were cut. Blamey also commented that "a tank without proper armaments is not worth producing".

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