Military vehicles do not simply appear, ready for production and use, out of some magician's hat. They have to be specially developed or at least modified from existing civilian designs or earlier vehicles. For many years, each new vehicle was assigned a number to help identify it which was prefixed with the letter T. Once it has passed all the tests required of it, it would often be classified as Standard in some form and assigned a new number beginning with M, though some limited procurement items went into production and use with the original T number. As improved models of the development vehicles often had additional sub-variants, which lead to improved subtypes of production vehicles and there were experimental improvements on the production subtypes, the result could be a long series of numbers and letters which described a specific item of equipment.

This was further complicated by the same basic numbers being assigned to more than one type of vehicle. Thus, T1 could be the designation applied to a tank, an armoured car, a scout car, a command car, gun and mortar carriers and others too. Following what each one was is not easy, and while many specialist equipment histories list those for a particular series obtaining an overview has often proved elusive. That is no longer the case, as David Haugh has not only researched the many series of experimental vehicles the US Army had over a third of a decade, he has also come up with photos of almost all of them. Some went on to greatness in production and worldwide service, such as the Tank, Medium, T6 while others such as the Car, Armoured, T17E1 and to some extent the T17E2 - but not the T17 or T17E3 - were built in some numbers and supplied to other nations.