June 1944
By the middle of 1944, as a result of his many conquests, German chancellor Adolf Hitler had the impossible task of defending the entire northwestern coast of Europe from enemy invasion. The Nazis knew an Allied invasion of occupied Europe was likely—Japanese diplomats stationed around Europe had chattered about an invasion in the Purple traffic since at least 1943—but they did not know when or where it would happen. For quite some time the Allies did not know, either.
Code breaking—of many kinds—helped cement the Allied decision. In November 1943, the Purple machine at Arlington Hall rattled out one of the most valuable contributions that Hiroshi Oshima, the Japanese ambassador to Nazi Germany, made to the American intelligence effort. It was a wordy, effusive, somewhat emotional, meticulous description of German fortifications along the northwestern coast of France, from Brittany to Belgium and everything in between.
Actually, it was a series of messages. The first was a missive in which Oshima bragged to colleagues in Tokyo about a trip he had taken to see Nazi operations in France. He and some colleagues had traveled by train from Berlin to Brest to inspect defenses there and along the French coast—what the Germans called their Atlantic Wall.
Oshima, who admired the Nazis, was full of details about who in the German Army was who—he described being “feted by Marshal Rundstedt”—and what an honor it had been to meet them. He reported that he and his companions had observed German defenses around Lorient, the Brittany seaport. They had seen night maneuvers; inspected encampments and harbors; spent the night in Paris; and gone on to Bordeaux, where they watched blockade runners carry out maneuvers. They headed to Poitiers and Nantes, meeting with German commanders. “When we were wined and dined we got the chance to talk with the right people everywhere.”
This dispatch was followed by a longer message, which was somewhat like reading the writings of a military tour guide. The gist of it was: As formidable as Hitler’s Atlantic Wall might be, it had sections that were less well protected than others.
“All the German fortifications on the French coast are very close to the shore and it is quite clear that the Germans plan to smash any enemy attempt to land as close to the water edge as possible,” Oshima reported with satisfaction. He said that “individual machine gun nests are, without stint, strengthened with ferro-concrete”; that in the event of an Allied landing, “naturally it cannot necessarily be expected that they could be stopped everywhere along the line; but even if some men did succeed in getting ashore, it would not be easy for them to smash the counterattack of the powerful German Reserves, who can rally with lightning speed.” He commended the “morale and military spirit” of the Nazi soldiers, who treated their weapons with “love and affection and also confidence” and went about their work cheerfully. “Everywhere I engaged in easy-going chats with the soldiers, and their respect and affection for Chancellor HITLER—the depth of it—I actually observed many times.”
He could not say enough about the soldiers:
The intimate unity—the complete unanimity of the German soldiers, high and low—the honest seriousness with which they apply themselves to their work is not only due to the general nature of the German people, but cannot but be regarded as also due to the Nazi education that they have received. This spirit permeates the very last soldier; I could see that and I breathed a sigh of relief and my heart was at rest.
Despite his infatuation with the Nazi troops and their training—or because of it—Oshima provided the kind of granular on-the-ground intelligence the Allies needed to defeat them. He noted that “the Straits area is given first place in the German Army’s fortification scheme and troop dispositions.” By this he meant the Strait of Dover, which is the narrowest part of the English Channel—the point where the crossing is shortest—connecting Dover in England to Calais, the French port. “Normandy and the Brittany peninsula come next in importance,” his message continued. “The other parts are regarded as only secondary fronts.” He then detailed where German troops were located, explaining that the army occupying the Netherlands stretched to the mouth of the Rhine; another army extended from there to west of Le Havre; and so forth. He provided a tally of divisions—infantry, armored, mechanized, airborne—and their strengths and numbers.
All of this was run through the embassy’s Purple machine in Berlin, transmitted to Tokyo, plucked out of the air by WACs working at the Vint Hill intercept facility, deciphered by the Purple unit at Arlington Hall—mostly young civilian women sitting side by side at a table in Building A—and rendered into English by linguists in the translating division. If Genevieve Grotjan had tied it up with a ribbon, she could not have made a prettier present to Allied military commanders. The messages were supplemented by others sent through the Japanese naval attaché machine being read by Frank Raven and his team at the Naval Annex. As it happened, Japan’s military attaché in Berlin, Katsuo Abe, was the polar opposite of Oshima; he hated and distrusted the Nazis and built his own spy network throughout France. So much the better for the Allies reading his dispatches. Raven and his crew called him Honest Abe, and what he learned about German coastal defenses also found its way to the D-Day planning operation. So did German Army Enigma messages read with the help of the bombe machines at the Naval Annex. At Bletchley, code breakers broke a long message from German field marshal Erwin Rommel, describing defenses along the Normandy beaches.
Together, the intelligence from these code-breaking efforts helped Allied commanders decide that they would concentrate their forces away from Calais, and make their D-Day landing in Normandy.