Within four months of the war’s outbreak the British were in possession of all three German naval codes. The Australians laid their hands on the code book for merchant shipping; the imperial naval code book was taken by the Russians from a cruiser which went aground in the Baltic; and the traffic signals book from a sunk destroyer was picked up in the nets of a British trawler. Listening stations were set up along the east coast, so that cross-bearings could enable the position of the vessel sending the message to be fixed, and the intercepted signals were analysed in a newly created
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