An enthralling examination on the impact that military intelligence had on the Second World War at sea. Perfect for readers of John Keegan, Max Hastings and Ian W. Toll.

How was the work of Alan Turing and other men and women at Bletchley Park used to influence naval strategies and shape the course of the war? And how did they use the information without alerting the Axis powers that their codes had been broken?

Shining a light on information that was previously kept secret from public view, Winton’s book assesses the impact of ULTRA and how the breaking of Enigma codes shaped Allied antisubmarine warfare in the Atlantic, convoy defence in the Arctic, amphibious assaults in the Mediterranean and attacks on heavy German naval vessels like Tirpitz.

‘This is a very good book; well researched, well written and well up the pecking order.’ The Naval Review

‘Altogether an interesting book which gives such a fascinating new perspective to events that one wonders why it has not been written before!’ Seascape International Maritime Magazine

‘Ultra affected almost every operation against the Germans at sea and hence this book is almost a complete history of the war at sea.’ Journal of Naval Science

‘… an excellent detailed examination of the practical application of Ultra intelligence in the war at sea’ Cryptologia

‘Until recently, no author has examined the impact of how ULTRA was used to win the battle for the Atlantic and adjacent waters. John Winton’s ULTRA at Sea addresses this imbalance.’ Military Review

‘Whether we like it or not, the Ultra story is a prickly one, and is at least changing the tones of the well-established picture we have of the Second World War.’ Navy News