Secret codes are as old as writing, but the science of codebreaking remained a minor field until the invention of the telegraph and radio made rapid communication easy, essential—and public.
This story has been told before, but science journalist Budiansky (Nature’s Keepers, 1995) tells it best. He has read the archives, interviewed participants, and seen newly declassified files. He begins in England. Capitalizing on their reputation (in Germany) for stupidity, the British assembled the world’s best codebreakers during WWI, routinely reading Germany’s diplomatic and naval traffic. In moments of leisure, they perused American communications, which were laughably crude (Woodrow Wilson coded and decoded his own messages). By the late 1930s, however, the US had reached parity with the British, and we could read Japanese diplomatic traffic—which was useful, but not useful enough to anticipate the attack on Pearl Harbor. Burned once, the Germans developed the famous Enigma machine, which created a cipher so complex that British and French experts were stumped. They were flabbergasted when the Polish secret service showed them one. It was not stolen; a Polish mathematician had recreated it from its pattern of transmissions, the first of many brilliant codebreaking coups that enabled the Allies to read large portions of enemy communications. Barely six months after Pearl Harbor, outnumbered US forces won a smashing victory at the Battle of Midway only because they knew every detail of the Japanese plan. The German naval command wondered why Allied convoys often sailed around waiting submarine wolf packs but remained confident its transmissions were secure. The codebreakers themselves were a collection of dogged obsessives, eccentrics, and mathematical geniuses who might work years to solve a single problem. The geniuses who worked on the Manhattan Project had easier problems because everyone knew an atom bomb would work. No one knew if a code was breakable until it was broken.
A marvelous history, full of color, drama, conflict, and tragedy. Besides being a terrific read, it illustrates one often overlooked reason why the Allieds won the war: they were smarter.