This book argues there is a special category of medium powers in the world - powers such as Britain, France, India, Brazil, Japan, perhaps China and others - which have sufficient military power to do something to protect their interests but which are not a match for the superpowers. It indicates that the uneasy role of medium powers, in the middle between the omnipotent superpowers and the virtually powerless small powers, at present ill-defined, should be thought through properly so that medium powers recognise clearly what they can and cannot do, which of their interests they can defend on their own and for which they need a superpower as ally. It surveys the whole range of naval warfare - equipment, operations, organisation and deployment - and discusses how each item should be tailored by the recognition of the position of a medium power. It considers alliances, a key element for medium posers and explores how these should be handled, how tight or loose they should be and what use they may be expected to fulfil.