I watched Bridge on the River Kwai with Alec Guinness years ago, a classic film made just 12 years after the end of the war in 1957 but in colour and not dated, as about the Japanese PoW's.
It's about a Colonel Nicholson who as the senior officer amongst the prisoners reluctantly agrees to camp commander Saito's suggestion of getting the World War II POWs to build a railway bridge. However, the project soon becomes an obsession..
The cruelty depicted at a time when it wasn't normal in British cinema to be so explicit was only part of the tale. Truly harrowing, brings home to you in a way no documentary really can, just how inhuman the guards were to other human beings, although in general the Japanese were brought up to think being taken prisoner was the ultimate degradation, worse than death, and prisoners were therefore the lowest of the low and should be treated as such.