The United States’ first attempt at a heavy tank came during the First World War with the Mark VIII or Liberty Tank, a joint-collaboration with the British and French. The US would subsequently adopt 100 of these vehicles. During the Interwar period, US interest in heavy tanks dropped significantly. The Mark VIII would be fully phased out by 1934 and the requirement for a heavy tank was removed from the Ordnance Book of Standards in May 1936. However, with the start of the Second World War in 1939, the process which would eventually lead to the M6 Heavy Tank began.
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