The A to Z Challenge asks bloggers to post 26 posts, one for each letter of the English alphabet, in April. Most of us choose to make these posts on a particular theme. My theme for 2022 is Codebreaking in World War II, which fits with the topic of the novel that I’m writing. Visit every day (except Sunday) in April for a new post on my topic.

O is for Baron Hiroshi Ōshima

Baron Hiroshi Ōshima was the Japanese ambassador to Germany during World War II. As a member of the Japanese diplomatic corps, he sent and received messages enciphered with the system that the Americans called Purple. William Friedman, with colleagues, broke Purple before the war began. Friedman wouldn’t have known at that time how important it would be for Americans to eavesdrop on Japanese ambassadors.

“Ōshima 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.” (p. 102, Code Girls by Liza Mundy)

In the fall of 1943, Ambassador Ōshima went on a tour of the Atlantic Wall, the German defenses on the coast of Europe. He sent a series of messages in November 1943, detailing the German troop locations with their strengths, numbers, and fortifications.

“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.”

These intercepts and others were used to help Allied commanders decide that the D-Day landing would be in Normandy, not Calais.

A dispatch from Ōshima on June 1, 1944, five days before D-Day, confirmed that Hitler had taken the bait of the fake army that I described yesterday.

“Ōshima added—and this was crucial; this was exactly what the Allies had hoped—that the Führer expected the real Allied attack, when it came, to come sailing through the Strait of Dover, toward the Pas de Calais.” (p. 305, Code Girls by Liza Mundy)

Ōshima was convicted of war crimes, but only served a few years. He lived in seclusion, dying in 1975, never knowing that his reports had been intercepted by the Allies and used to win the war.

Most of my information came from Code Girls by Liza Mundy. The Wikipedia article was also helpful and it led me to a book that I might read in the future: Hitler’s Japanese Confidant: General Hiroshi Ōshima and Magic Intelligence, 1941-1945 by Carl Boyd.