In spite of all that has been written about every facet of World War II, there is still a good deal of mystery surrounding the basic operation on which the Normandy invasion was built- what is known in military jargon as ""Mulberry"". Here is that story, told with the vividness of an eye witness, and the courage not to pull punches where some of the personalities and the difficulties are concerned. ""Mulberry"" was the building of piers and breakwaters for an artificial harbor- one for the Americans, one for the British landings. The story, based on confidential records as well as first hand knowledge (the author is Commander Stanford, U.S.N.R.) goes back to the initial conception, the building of the equipment, the hurdles taken (despite security wrangles, unclear responsibility, a scrambled chain of command, untried engineering experiments and problems of unfamiliar tides and unknown defenses). The personnel requirements were themselves an enormous headache. Experts on tugs, on salvage, had to be brought in. Last minute tests showed necessity of structural corrections. And when the operation wa in actual otion, there was the initial debacle of the first siting and the necessary improvisations. Captain Clark proved an inhuman driving force, achieving the impossible, but at terrific cost to man power and morals. Then came -- after two days success- the crippling storm and the subsequent destruction. But the concept and its initial execution made the invasion, costly as it was, possible. And this story, to be illustrated with photographs and diagrams, and with an introduction by Samuel Eliot Morison, will take its place in the important annals of the war. For the layman as well as the expert.