Never before, he pointed out, had a team of cryptanalysts managed to reconstruct a machine that nobody, apart from the enemy, had laid eyes on.
And here is the other thing: The Purple cipher didn’t just give the Allies insight into Japanese thinking. As Friedman pointed out, the ability to read messages produced by the Purple machine provided “the most important source of strategically valuable, long-term intelligence” available to the Allies as World War II unfolded, including the thinking of fascist and collaborationist governments around all of Europe.
The team’s breakthrough was held in the strictest secrecy. They would receive no public recognition. Only a handful of people could know the Purple cipher had been broken, because if the Japanese learned what had been accomplished—or even got an inkling—they would stop using the machine.
The code breakers took a week to test their discovery. Friedman then shared their success with the small number of officials in military intelligence and Roosevelt’s inner circle who were entitled to know about it. His private announcement was made on September 27, 1940, the day that Japan signed the Tripartite Pact, signaling that the world’s belligerent nations would “stand by and cooperate” in pursuit of their “new order.”
Within two weeks the code breakers built a facsimile of the Purple machine. Streams of messages were pouring in from Japanese diplomats in Berlin, Rome, Warsaw—all the key rumor capitals of Europe. Often they were reporting back to Tokyo on conversations with Axis leaders. The messages were lively, opinionated, and informative. They were full of detail and often went on for pages.
For most of the war, it would be the Japanese Purple machine that gave Allied nations their best information about what was being thought and said—and purchased and developed and manufactured—in Europe, especially Germany. This was largely thanks to General Baron Hiroshi Oshima, who served as Japan’s ambassador to the Greater German Reich. Oshima was a former military man and confidant of Adolf Hitler who enjoyed wide-ranging talks with the Führer. The Japanese ambassador admired the Nazis, toured German military facilities, and wrote reports back to Tokyo that were long, erudite, and precise. Oshima’s painstaking description of German fortifications along the French coast would be invaluable when Allied commanders were planning the D-Day invasion.
All of the dispatches were frank, written by men who had their ears to the ground all over Europe. Going forward until the end of the war, the Japanese diplomats used the Purple machine to convey what Hitler was saying to his French collaborators; what people on the streets of Europe were feeling; what newspapers were writing; what Albert Speer, Nazi minister of armaments and war production, was reporting about munitions; what transpired when a team of German officers tried to assassinate Hitler. (“What was really mysterious was the fact that the Chancellor, who was nearest to the bomb when it exploded, was unhurt with the exception that his clothes were torn to pieces by the blast and he sustained a few burns,” reported one Oshima message.)
Early in 1941, several members of Friedman’s team quietly boarded Britain’s newest battleship, the HMS King George V, which had stopped in Annapolis to drop off the new British ambassador. They stowed one of their precious homemade Purple deciphering machines, hidden in a crate, on board, and—at great peril—took it across the sea, passing through the rattlesnake nest of lurking U-boats and presenting it to their astonished British colleagues.
Read today, the language in the diplomatic messages feels fresh and intimate and vivid. To take an almost random sample, consider a series of messages sent in 1943 between Japanese diplomats in Europe, writing to one another and to their home office in Tokyo, using the Purple machine and a few other diplomatic ciphers.
“England and America are jingling money in their pockets,” wrote Tokyo headquarters to the Japanese ministry in Madrid, at a time when Spain’s putative neutrality was in question and the Allies were trying to prevent Spain from entering on the side of the Axis. “We have got to make Spain change her mind right away if we can.”
“This London report twisted the facts, presumably to give the impression that there is a serious rift between Finland and the Axis,” wrote Helsinki to Tokyo.
“HITLER said, ‘When this war is over, we Germans are going to start founding a new Europe,’” reported the Japanese ambassador in Vichy France. Pierre Laval, a top French official in the Vichy government, then “retorted coldly: ‘Why not found a new Europe first?’”
“The enemy’s air bombardment of all Italy is being carried out with extreme violence,” Rome wrote Tokyo.
“I would say that if this time Germany does not win, the song will be out and the jig up,” warned Oshima from Berlin, as Germany girded itself for an effort to capture Leningrad and push its offensive in Russia.
“Passing over French territory night after night, British and American planes wreak havoc on Italy without any signs of a let-up,” reported the ambassador in Vichy. “The French people have always fervently hoped for a victory for the British and Americans, and now they revel in the conviction that such a victory is coming sure as death.… Also, this business of sending Frenchmen to work in Germany is heinous to the French.”
“Now that the Axis forces have been cleared out of Africa the question of an Anglo-Saxon invasion of Europe has become very real,” Vienna warned Tokyo.