Puzzles and codes have multifaceted uses in practices of concealment, especially for militaristic purposes, corporate secrecy, or national security.The term ‘Enigma’ is perhaps most recognisable in modern history and contemporary culture as the name of a cipher device used by the German military to send messages during World War II. This chapter moves to the historical context of the twentieth century and shows how humans sometimes deliberately engineer enigmas to serve their own purposes. The author focuses on the mathematics underpinning the story of the Enigma Machine, setting out the process both of the code’s creation and of its decryption. Following the story of Alan Turing, a mathematician and one of the code breakers at Bletchley Park, the chapter emphasises both the necessity of collaborative labours to solve challenging problems and the importance of individual research and investigation to resolve crucial pieces of a much larger puzzle.

At first glance, the Battle of the Atlantic appears to be the arena of war most likely to provide a trigger for a German declaration of war on the USA. The US Navy had been establishing a presence in the eastern half of the North Atlantic with increasing assertiveness since April 1941 and even began escorting British convoys in mid-September 1941. Historians attempting to integrate these events into Hitler’s decision to declare war on the US fall into two different camps. One see in it an unavoidable reaction to the presence of US escorts who were stymying the efforts of his U-boats to get at the convoys, while other maintain the he was longing to unleash his submersibles at the vulnerable merchant traffic in US waters.

I am now in a position to prove that neither was the case. US escorts only rarely had to prove their worth, because of the low number of convoy interceptions between July-December 1941 – a direct consequence of the rerouting of convoys thanks to the work done in Bletchley Park. Also, not a shred of evidence exists to suggest that either Raeder or Dönitz regarded patrols to the Americas as a missed opportunity.