Could it be, he was in direct contact with FDR and executed Operation Tora? Climb Mount Niitaka happened for a reason and it wasn’t Japanese.
At the same time as the attack on Pearl Harbor the Japanese also attacked US airbases in the Philippines and targets in British Malaya and British Hong Kong.
Was Yamamoto also in command of these forces?
It was his plan, overly complicated with to many moving parts, typical of imperial Japan. The admiral promised 6 months of victories for the imperial army. He delivered as promised, After 6 months Midway happened, followed by three years of defeat as the great admiral predicted.
Japan didn't really have any choice but to go war. The FDR Regime made sure of that.
The only choice the Japanese had was to go either south for the oil fields in the Dutch East Indies or north into Siberia. The Japanese Army was recently defeated by the combined Soviet and Mongolian Army during the Battles of Khalkhin Gol on Manchuria-Mongolia border region so they believed it was easier to take on the British and Dutch with the Japanese Navy. Soviet spy Richard Sorge also had a hand in convincing the Japanese that he attack south was the better plan.
It turned out to be a fatal mistake.
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