In May 1941, at a time when the Second World War was in full swing and the British forces were doing their utmost to block Hitler’s rampage across Europe, the battle to control the ocean was of paramount importance. Convoys of ships transporting troops and bringing much-needed supplies and materiel to Britain from the USA and Canada were routinely hunted down and attacked by groups of German submarines, known as wolf packs, causing untold damage to the British navy and mainland, not to mention suffering and death to the sailors manning those ships.
The British war effort was conducted on a number of fronts, among them that of intelligence. Inter alia, the British were doing their utmost to decipher the codes used by the Germans to disseminate their military messages to their troops, whether on land or at sea, but their efforts were frustrated by their inability to gain access to the encoding machine used by the German for this purpose. The existence of the machine, known as Enigma, was known to the Allied forces, but without a working exemplar it was impossible to ascertain precisely how it was used. Although the Poles and the French had managed to work out some aspects of the code, they were still far from attaining perfect knowledge of the way the machine worked. The British had set up an extensive system for decoding and translating messages at Bletchley Park, and tremendously important espionage work was implemented there, including the development of what came to be known later as the first computer, by Alan Turing. As is well known, Turing played a seminal role in understanding the workings of the Enigma machine and deciphering the code.
How the actual machine came to be in the hands of British Intelligence is the subject of this book, which tells an exciting tale of the pursuit and capture of a German u-boat by a British destroyer. HMS Bulldog, commanded by Captain Joe Baker-Cresswell, as he shepherded a convoy of merchant ships across the North Atlantic. From being the hunter he became the hunted, but the depth charge he set off succeeded in hitting the German u-boat that was pursuing his vessel. The u-boat was listing, and its crew abandoned ship. At that point Captain Baker-Cresswell decided that instead of finally sinking the German vessel his men would board it and take whatever they could find, known as ‘doing a Magdeburg,’
The operation was complex and risky, as the u-boat was in the process of sinking, but the men of the boarding party were determined to remove anything they could find that looked as if it might be of value, whether papers or equipment. Thus it was that one of the men came across what looked like a peculiar typewriter which was bolted to a wooden surface. Using the screwdriver that he had included in his bag of tools before leaving the ship, the officer managed to release the machine. It was only with great difficulty and considerable dexterity that the men managed to haul the heavy machine up to HMS Bulldog, where it could finally be identified as an actual Enigma machine. Displaying great bravery, the boarding party returned to the u-boat several times to remove whatever they could find that might be of value to the war effort.
The commander began towing the captured u-boat back to Blighty behind his ship, but when it began to sink beneath the waves he cut the tow-rope and let it go to the bottom. The operation was later given the name ‘Operation Primrose,’ and every effort was made to ensure that the Germans did not realise that the British had managed to seize hold of an actual working Enigma machine. In fact, Winston Churchill kept the details secret for months even from his close ally, President Roosevelt. The decryption of the Enigma code enabled the British forces to anticipate the movements of the u-boat wolfpacks, significantly reducing the loss of ships and contributing significantly to the victory of the Allies.