Operation Primrose

Operation Primrose follows the capture of German submarine U-110 in May 1941, when a British boarding party seized an intact naval Enigma machine and crucial code material before the submarine sank. Boyle explains how the intelligence windfall fitted into the wider cryptographic struggle between the Royal Navy, Bletchley Park and Karl Dönitz’s U-boat command, and why naval Enigma had been especially difficult to penetrate.

The book then connects the intelligence contest with the pursuit and destruction of the battleship Bismarck later that month. By bringing submarine warfare, codebreaking and surface operations into one narrative, Boyle shows how information gathered at sea could influence the Battle of the Atlantic and how small operational opportunities produced consequences far beyond the ships immediately involved.