As an aspiring student of German history, I've recently been reading a fair bit about the 1960s trials of Nazi criminals in the West German legal system, most notably the trial of over 20 former Auschwitz staff in Frankfurt. I know that a large number of Japanese war criminals were prosecuted by the International Military Tribunal of the East and individually by many allied powers, but did the domestic Japanese legal system itself ever conduct any investigations or prosecutions of war criminals who escaped justice? Cursory google searches have yielded little results, and I suspect the answer is no.
Yes - and no.
General Headquarters GHQ never dismissed the Japanese government, which was the original plan. An extensive military government had been assembled, mostly at the Presidio of San Francisco, but after landing in Japan for some reason MacArthur changed his mind.
So, GHQ left the Japanese government in place, which had various ramifications.
When GHQ decided on the 'removal and exclusion' of undesirables from the government, meaning ultranationalist and militarists, the "decision" to support that policy was signed by the Emperor himself, countersigned by the Prime Minister and key Ministers, and announced in the official gazette. GHQ made lists of positions in organizations that were banned, and the Japanese government helped identify them. These were done through Supreme Commander Allied Power Instructions called SCAPIN. There was a separate group for administration called SCAPIN-A.
In the event of banned organizations, they were directed to disband, and they turned in their funds and property to the Japanese government, which liquidated property and deposited any funds in the general coffers.
The Occupation forces' military police (mostly US Army) arrested the Class A, B, and C war criminals. The Class G war criminals were mostly a paperwork drill of identifying people, mostly by positions in banned organizations, and publishing notice of their lifetime bans from public office in the Official Gazette. The Japanese government argued for and then helped administer an appeal application and process under which someone could argue that the facts were wrong or that somehow they should not be punished.
The system worked well to identify most everyone of consequence in the wartime military or government, so nearly no Japanese seemed to want to exceed what was done.
One of the odd events was the massive Dai Nihon Butokukai the Great Japan Martial Virtue Association. The story is too long to convey, but GHQ directed the Japanese government to ban everyone member. When it realized that meant that most every able bodied man in the government, police, courts etc would be banned, the Japanese government banned it under a different law than directed, one that meant that every single man would have to be vetted personally rather than banned as a class. It was a fascinating example of the near powerless Japanese government using administrative jûjutsu to go against GHQ directions.
As it's a key development in Japanese martial arts history, we'll go into the incident in some detail later in The Kanô Chronicles® www.kanochronicles.com