This book deserves more than five stars, and the massive British and American government information releases that made it possible also deserve credit for making the book possible.
This book pays the reader the compliment of assuming both intelligence and sincere interest in the subject. Although much of the book is a repeat of what has been written before, the book also contains much new information (especially about breaking the Japanese codes) and important insights. As the most complete examination of the code side of World War II, the book is essential reading for anyone who is interested in that conflict.
Although this book is about World War II, it contains much interesting material about earlier code-breaking, especially during World War I and the disarmament conference in the 1920s.
Basically, codes and codebreaking were in a transition period during the 1930s and 1940s between the primitive historical codes and the modern encryption techniques. The weakness of this transition period was that computer-like devices could use brute force calculations to spot patterns that the code designers were unaware of.
Clues came from many places. For example, "eins" showed up very frequently in German communications, so by looking for four word groups of great frequency, you could guess that they meant "eins" and work from there. This could unmask the daily code key much faster. Luftwaffe code operators were sloppy about the codes they used, and those bad habits provided clues as well. The British were brilliant in targeting German naval and weather vessels, and sinking them in ways so that codes and code machine parts could be saved. In some cases, Japanese embassies were broken into and codes directly stolen.
The most fascinating parts of the book come from the descriptions of how raw brain power solved problems. Many new code-solving techniques were developed. The Poles (especially Marian Rejewski) deduced the structure of the German Enigma machine just through examining the encoded message structures, and built one. Later, Turing took the idea of linking Enigma machines together to test patterns and developed a process for finding which settings were being used each day. Almost unbelievably, ideas and machines came along later that greatly improved the efficiency of this process even further.
If you like puzzles, you will love the discussions of the codebreaking technques because they employ detailed descriptions of the codes, code machines, and the exact methods used. Many wonderful diagrams of wiring and logical connections make this transparent for those who are interested in fully understanding. If you are not so interested, you can skip ahead to the material that interests you instead.
Emotionally, you will find yourself riveted by the races between the code breakers and the pace of unfolding battles. In several instances, such as at Midway, in the North Atlantic convoy runs, in North Africa, and during the Battle of the Bulge, the codebreakers played a decisive role. You will be intrigued by how many military leaders were reluctant users of this intelligence. Does Monty come to mind? You will never think about the events in World War II in the same way, after fully understanding what was known and not known by government and military leaders.
New light was shed on major controversies for me in this book. A famous one surrounds whether FDR knew of the attack on Pearl Harbor, and used inaction to manipulate entry into World War II. From a codebreaking perspective, it is clear that the U.S. knew that the Japanese were going to break off diplomatic relations, but little else. There were indications that an attack was coming, but no knowledge that it was aimed at Pearl Harbor.
On the other hand, decoded radio transmissions from German police units clearly indicated that massive numbers of Jews were being killed during the invasion of Russia. This material was probably read by Churchill. It is not clear who else read it. Those who are interested in what government should have been doing about the Holocaust will find much troubling evidence of government's knowing inaction in this book.
The many bureaucratic battles detailed here to take over codebreaking and to get the credit for it are worth the price of the book by themselves. For example, there is a fascinating story of how the key person in the codebreaking for the battle of Midway, Commander Joseph Rochefort, ended up running a dry dock on the west coast soon thereafter, far away from codebreaking for the rest of the war.
007 fans will enjoy the many references to the war-time activities of Ian Fleming in dreaming up schemes to help the codebreakers.
After you finish reading and thinking about this fascinating book, I suggest that you consider how you can overcome the vulnerability that you have to someone breaking into your communications. How can and should you be using encryptian today? This book won't answer those questions, but you should be asking them and looking for answers.
