David Bergamini was the first AFAIK to suggest the Showa Emperor (Hirohito) was the driving force behind the war in general and the war in the Pacific in particular, at a time when Edwin O. Reischauer had spent 20 years peddling the idea that the Emperor had been co-opted by a bunch of “militarists,” in large part because WWII morphed into the Cold War and we needed Japan to be our forward megabase against the Soviet Union and China in east Asia.
I have his book, which wasn't all that easy since I was living in Japan at the time. It has been furiously denounced as a "polemic", "debunked", and "historically inaccurate" by the usual apologist "experts", but those few items I was able to check on, checked out. Not sure just what to say about it, but if Bergamini was correct about his principal thesis, Hirohito was at least aware of the planning long before the attack took place, more so than Tojo, who wasn't considered reliable at the time and swung for it later. (He had it coming, too, but not necessarily for that.)
Bergamini and his mother, father, and sister were prisoners in a Japanese concentration camp in the Philippines for the duration of the war, which may have influenced his attitude a little (yeah, just a bit) and the general consensus that his scholarship is suspect is not something I trust any more uncritically than I do his thesis. Japan is, even now, a very closed society at the upper strata.