Ultra at Sea: How Breaking the Nazi Code Affected Allied Naval Strategy During World War II

207 pp. Includes black-and-white photographs. "...the first detailed examination of how Ultra intelligence obtained from Enigma was used to win the war at sea. Winton describes in exciting detail the way Ultra was used in the cat-and-mouse chase that led to the sinking of the Tirpitz and the Scharnhorst, two German battleships in the North Sea. In addition, Winton explains how carefully Ultra was used in order not to arouse Nazi suspicions that Enigma had been broken. He shows how an incident involving intelligence given to the French seriously compromised Ultra. He also shows how certain episodes resulted from the judicious decision not to use Ultra: For instance, in February 1942, three German battleships were allowed to pass through the Straits of Dover in broad daylight; it was the first time since 1690 that major enemy warships passed so close to the English coast."