Even in the mid 19 forties, it looked barbaric. A british or american soldier who fell into japanese hands had a 27 % chance of dying before being returned home. It's not even close. The number of peop who died in japanese captivity compared to the number of people who died in german or italian captivity is huge.
Japan's rising sun goes supernova and engulfs a huge area of Asia and the Pacific. A war without mercy begins to develop infusing the whole conflict with a savage vibe.