Ōshima made visits to the Eastern Front and the Atlantic Wall, and he met periodically with Hitler and other Nazi leaders. Being a meticulous military officer in training, he wrote detailed reports of the information provided to him by the Nazis. The reports were sent by radio to Tokyo in the Purple diplomatic cipher. Unknown to the Japanese, the PURPLE cipher was broken by American codebreakers in 1940. Thus, Oshima's reports were read almost simultaneously by his superiors in Japan and by Allied leaders and analysts as "Magic" intelligence. Sometimes, the Allies read the reports before the Japanese did, as transmission problems between Germany and Japan often held up the reports for hours.