He had a weapon ( special bombs designed to deliver millions of plague bearing fleas) all developed at special bases in Manchuria. Which housed camps of US and Chinese prisoners on whom bio weapons were tested.
All he lacked was a long range delivery system. The Japs had prototype aircraft but had not yet gone into production. What stopped this. The US bombing of Hiroshima.
Shiro Ishii. Tortured and killed hundreds of thousands including US POW Never prosecuted for war crimes.
( History Channel. Secrets of the Axis)
“special bombs designed to deliver millions of plague bearing fleas”
Operation Cherry Blossoms at Night was suppose to attack Northern California