The overriding anxiety of the British during World War II was their mastery of the ocean routes and the free approach and entry to their ports. To maintain this mastery and freedom, the Admiralty belatedly in 1939 combined all its intelligence outfits into one giant complex (housed in very small quarters), the Operational Intelligence Centre. Formerly, the left hand of cryptanalysis knew not what the right hand of aerial observation was up to, nor were the reports of ships at sea, of secret agents abroad, of intelligence from the Army and the Foreign Office at all coordinated into one massive vision of intelligence data. (Back in World War I, naval conservatism had ruled out the very idea of ships being directed by men who might never have had seagoing experience.) To do some good, the O.I.C. not only had to analyze information but also get it out again. Once the Atlantic U-boat code (a machine cipher) had been broken, the Germans were haunted by a single commanding mind reading their own. Accurate and rapid intelligence led to the O.I.C.'s first self-justifying feat, the pursuit and sinking of the battleship Bismarck. Beesly, who was in the O.I.C. from 1940-45 and had access to information only now declassified, tells the full story for the first time of the Battle of the North Cape, the end of Scharnhorst and Tirpitz, and the defeat of Admiral Donitz. No spellbinder but gutsy and lively.