Corbett looks at the theory of war, and then the theory of naval war: from grand strategy to strategy. He looks at how England, with an active naval policy, was able to prevent often stronger nations and navies from ever landing successfully, or cutting supply routes from colonies and empire. The object of naval warfare, which made the foregoing possible, depends upon control of the sea, although not necessarily on omnipresence. A mere threat often suffices. 'By using the history of navies to good effect, Corbett illustrates his points clearly and well: naval strategy and tactics is often regarded as somewhat specialised for the general reader of military history, but Corbett makes the subject easy to understand, yet emphasises the complexities of his subject without recourse to jargon or technobabble.'In all this is one of the important books on the subject, and is well worth reading even if it is not relevant to one's field of study in any way.