After the battle of Jutland, Churchill remarked that Admiral Jellicoe was the only man who could have lost the war in an afternoon. That seems rather unlikely, but it’s certainly true that the sea power exercised by U-boats could well have determined the outcomes of both world wars — at least as far as Britain was concerned. In the Far East in 1945, Admiral Chester Nimitz’s signature on the Tokyo Bay surrender document concluded the most ingenious campaign in military history, celebrating an apotheosis of American sea power.

Sea power bulked large during the Cold War, contributing to Nato’s maritime strategies and to the nuclear deterrent postures of both blocs. Since then Francis Fukuyama has proposed The End of History and Professor Philip Bobbitt’s recent Terror and Consent has explained the new paradigms of conflict.

After a century of such evolution, where stands sea power today? People watching Afghanistan and Iraq on British TV might be forgiven for believing that it’s all over — battlefleet will never again confront battlefleet and for Britain to spend on a couple of aircraft carriers is a hubristic extravagance.

Issue One of Jane’s World Navies provides an interesting corrective. This 450-page country-by-country analysis goes well beyond simply enumerating hardware. It analyses capability, quality, interoperability, civil-military relations and describes recent deployments, tasks and operations. Each “assessment” section is an excellent description of the nation’s needs, intentions and strategies.

The overall impression is one of buzzing activity. For sure, battlefleets don’t confront each other any more, but the multiple objectives of maritime power include humanitarian and environmental tasks, customs and littoral policing, narcotics interdiction, protection of fisheries and trade, nuclear and conventional deterrence, anti-terrorist measures, exercises with allies, and anti-piracy operation and a wide range of military tasks in support of land forces.

Of the 169 countries considered, 25 are without a navy, having no coastline or because of other factors. The rest divide roughly into those that concentrate on local sovereignty issues and those that aspire to a power-projection role. Even small nations’ patrol boats can pack a big punch. Jane’s World Navies shows that the microchip age has made weapons and surveillance systems very smart indeed.

Among the numerous pressure points discussed is the Strait of Hormuz, controlled by Iran’s Russian Kilo-class submarines, advanced C-series Chinese-supplied missiles and a sophisticated minelaying capability. Little Oman is on tiptoe opposite. China already owns nuclear-powered submarines and it is increasingly clear that she intends to build indigenously designed aircraft carriers. A detailed exposition of her regional organisation covers her quiet military expansion into the disputed Paracel and Spratly islands. In February 2007 Russia unveiled a big rearmament programme, a quarter of the budget allocated to the navy.

Illustrative of the other end of the spectrum is the news that the Trinidad and Tobago Coastguard is to be upgraded against the “war on drugs”, funding provided by Australia’s export credit agency.

What of Great Britain? “The Royal Navy remains arguably the world’s second navy in terms of capability and activity — if not in terms of size” and “although not widely recognised, the navy’s contribution to Iraq and Afghanistan has been considerable”.

The editor Eleanor Keymer and her team are to be congratulated on a splendid product of great general interest.

Details of Jane’s World Navies and other Jane’s publicationsmay be found at www.janes.com