We Watch, We Track, We Hunt, but Code-Breaking Makes the Kill

The recent reports that the United States intercepted and broke Iranian communications codes serves as a reminder, once again, that code-breaking is the most trustworthy, high-level, voluminous, continuous, unmediated form of intelligence available. Despite all the talk about the importance of “human intelligence” that followed George Tenet’s resignation last Thursday, the reality is that throughout history, no other form of intelligence -- spying, interrogations, reconnaissance -- has ever achieved such a level of success.

In World War II, for example, the Poles cracked and the British expanded the solution of the German Enigma cipher machine. This allowed them to decrypt radio messages from Nazi U-boat headquarters in occupied France, revealing submarine “wolf pack” locations to the Allies, enabling convoys to steer around them and minimize their losses.

The reading of German espionage messages also suggested to the Allies what kind of false information the Germans would accept based on their preconceptions and so helped trick the Nazis about the location of the D-day landing.

In the Pacific, the U.S. Navy’s solution of Imperial Japanese navy cryptograms helped defeat the forces of Adm. Isoruku Yamamoto at Midway -- halting Japan’s hitherto unstopped advance. And the breaking of the Japanese army’s water transport code revealed the noon position of many Japanese convoys. This enabled American subs to sink much of Japan’s merchant marine fleet, all but bringing that nation to its knees even before the atom bombs were dropped.

Code-breakers demonstrate their abilities most dramatically in wartime. But they play a role in peacetime as well.

During the Washington naval disarmament conference of 1921-22, for instance, American code-breaker Herbert O. Yardley and his team read the coded dispatches of Japanese diplomats. They revealed that, if pressed, Japan would yield on its position for more warships than the United States wanted it to have. Knowing this, America pressed -- and got what it wanted.

Why is code-breaking so important? Why has it outperformed other forms of intelligence throughout history? Reports from a spy were slow, subjective, even suspect: Was he telling truths only to set up a deception? Prisoners of war usually knew only their units and an occasional tactical plan. Reconnaissance, even aerial photography, could report only what it could see; prediction required inference.

Code-breaking, by contrast, handed over the very words of the enemy, without an intermediary, often at a high level. It sticks your head into the other side’s huddle.

Communications intelligence has been sought ever since modern diplomacy evolved in the Renaissance: Specialists in candlelit chambers slid hot wires under wax seals and opened ambassadors’ dispatches. But it was not taken very seriously by the generals -- and was, indeed, not all that important -- until radio came into widespread use during World War I.

Germany, for instance, solved Russian radio cryptograms on the Eastern Front from 1914 to 1917, helping it to defeat the czar’s armies and leading eventually to the Communist revolution. British reading of German naval messages helped the Royal Navy bottle up the German High Seas Fleet for much of the war. France’s solution of Germany’s ADFGVX field cipher enabled it to block the kaiser’s supreme offensive in March 1918.

And six weeks after President Woodrow Wilson made public Britain’s solution of German Foreign Minister Arthur Zimmermann’s coded proposal to Mexico to join in a war against America -- the greatest intelligence coup of all time -- the U.S. declared war on Germany.

At last the generals understood: Code-breaking mattered.

Countries that did not have cryptanalytic agencies before the World War I -- Britain, Italy, Germany, the United States -- established them afterward. Thus code-breaking brought all intelligence into significance. It confirmed its usefulness in World War II and afterward. Which is one reason America’s present communications intelligence body, the National Security Agency, is today bigger -- and probably more productive -- than the CIA.

David Kahn is the author of “The Codebreakers” (Scribner, 1996) and “The Reader of Gentlemen’s Mail: Herbert Yardley and the Birth of American Codebreaking,” published in March by Yale University Press.