The Imperial Japanese built a heavy water plant in 1936 . How different Pearl Harbour would look if they had of been successful in building a device.
If they had of built a device and a means of delivery the outcomes would have been different.
The research done by them in Camp 731 was interesting from a historical point of view . Technically not very highly advanced , but an interesting inquiry into human indifference to pain and suffering in the search for new weapons .