The object of this book is to provide a comprehensive account of the technology of tanks, the tracked armoured fighting vehicles which have become such an important element of military power. The account is concerned primarily with the current state of tank technology. But it also covers preceding developments, to help the understanding of how. or why. tanks have taken their present form while other forms or concepts have been abandoned. It also includes an outline of the evolution of tanks from their inception, to put their current state in its historical perspective and in the process to throw additional light on their origins, about which there is still some confusion.