To Fight or Not to Fight: The Role of Intelligence in Japan’s Decision for Pearl Harbor

“I was shocked to the point that I was blinded by sheer disbelief … In the end, [the U.S.] completely disregarded the years of sacrifice made by Japan, forcing us to forgo the great nation status that we had striven so hard to establish in the Far East. But to do so for Japan was none other than committing suicide. We now had no choice but to rise…
(From Jidai no Ichimen [An Aspect of Time], 2 vols, Tokyo: Hara Shobo, 1985.)

If there was a Rubicon in the path to Pearl Harbor, it would most certainly be November 26, 1941, the day when Togo Shigenori – the leading proponent against war – lost all hope for peace and felt that Japan now had to rise. Of course, Togo was no pacifist, but at the same time he was quite cognizant of the fact that a war with the U.S. could not be won. If so, then what forces pushed Togo toward to this tragedy? Was it, as many have claimed in the past, because the so-called Hull Note was so uncompromising that it basically amounted to an ultimatum?

In light of recent revelations in prewar Japanese SIGINT documents from the US National Archives, the National Security Agency archives, the Japanese Diplomatic Records Office, and the British National Archives, the purpose of this presentation will be two-fold: first, to provide a brief overview of the obscure history of the Japanese Black Chamber; and second, to examine/evaluate the role that intelligence played in decision making in Tokyo during the particularly critical juncture of November 1941 when the U.S.-Japan talks were being. In conclusion, a more viable alternative explanation behind the Togo hensetsu (volte-face) will be given which will lead to a greater insight into the complex chain of events which ultimately led to the fateful decision to go to war.

Tosh MINOHARA is Professor of Diplomatic History at the Graduate School of Law at Kobe University. His primary research focus is on U.S.-Japan relations and has numerous publications including: “The Japanese Exclusion Act and U.S.-Japan Relations: The Truth behind the ‘Grave Consequences’ of the ‘Hanihara Note’” (Iwanami Shoten, 2002) [Shimizu Hiroshi Book Award], The Anti-Japanese Movement in California and U.S.-Japan Relations: The Friction between Japan and the US over the Immigration Problem in 1906-1921 (Yuhikaku, 2006), Japan’s Major Policy Issues, 2000-2009: From the Perspective of Diplomacy and Security [editor and contributor] (Kashiwashobo, 2011), An Alternate History of Japan-US Exchanges: Reading the 20th Century in Materials of the America-Japan Society” [co-editor and contributor] (Chuokoronshinsha, 2012), The 100-year History of the Japan-US Relations surrounding ‘War’: From the Russo-Japanese War to the War against Terrorism [editor and contributor] (Asahi Shimbun Press, 2012), Tumultuous Decade, Empire, Society, and Diplomacy in 1930s Japan [co-editor and contributor] (University of Toronto Press, 2013), and The Decade of the Great War: Japan and the Wider World in the 1910s [co-editor and contributor] (Brill, 2014).