Virtually all of Ōshima's dispatches were intercepted: approximately 75 during the 11 months of 1941, some 100 in 1942, 400 in 1943, 600 in 1944, and about 300 during the just over four months of 1945 when Germany was at war. For example, in a dispatch decoded on 19 January 1942, Ribbentrop agreed to supply daily intelligence reports to Ōshima, which he could pass on to Tokyo. He warned that "any leakage of these reports due to our fault would be of grave consequence, so all the handling of these reports should be strictly secret". This despite the fact that the Germans often reproached him of the unreliability of the Japanese codes, although Ōshima assured them of its security. This laxity proved to be fatal to Japanese espionage efforts, as even much of the intelligence gathered by the Japanese spy network codenamed "TO" in Spain (with implicit support given by the Spanish authorities) was channelled through him. This evidence halted the loading of petroleum by the United States onto Spanish tankers in 1944.