The sea has always been central to human development as a source of resources, and as a means of transportation, information-exchange and strategic dominion. It has been the basis for our prosperity and security. This is even more the case, now, in the early 21st century, with the emergence of an increasingly globalized world trading system. Navies have always provided a way of policing, and sometimes exploiting, the system. In contemporary conditions, navies - and other forms of maritime power - are having to adapt, in order to exert the maximum power ashore in the company of others and to expand the range of their interests, activities and responsibilities. Their traditional tasks still apply but new ones are developing fast. This updated and expanded new edition of Geoffrey Till's acclaimed book is an essential guide for students of naval history and maritime strategy, and anyone interested in the changing and crucial role of seapower in the 21st century.