The Germans granted the Japanese ambassador, Baron Hiroshi Oshima, the intimacies of an ally, and, as a former military attaché', he took considerable interest in the military sphere. Toward the end of October, 1943, when it became evident that the Allies would invade Europe and the Wehrmacht had begun to stiffen its defenses, Oshima toured the Westwal and the Siegried Line. He reported on these preparations in great detail in a long radiogram of between 1,000 and 2,000 words.
As a powerful German station pumped it into the ether for the 5,000-mile leap to Tokyo, a new American intercept post at Asmara, in the former Italian colony of Eritrea bordering the Red Sea, picked it up. Back the cryptogram went to the Signal Security Agency. It proved to be in PURPLE, which the American cryptanalysts read with relative ease. The solution went to General Dwight D. Eisenhower's headquarters, where it shaped basic strategy for the conquest of Germany. "