The Japanese soldiers were so cruel during WWII that it beggers belief.

There is a tendency in fiction of authors trying to be impartial when depicting historic conflicts. In the 2007 film Letters from Iwo Jima we follow a sympathetic group of Japanese soldiers trying to survive in the final days of the war. They’re caught between an oppressive government, insane officers, and American soldiers more than willing to commit war crimes.
It’s a great film. And a lot of it is historically accurate. But it leaves out a lot of context in order to make its protagonists sympathetic.

It leaves out the “comfort women”, the countless women forced into sexual slavery by the Japaneae military. It leaves out the beheading contest held among officers that ran in public newspapers. It leaves out the abuse of prisoners. The crimes of Unit 731. The 50,000 Chinese killed each day in the lead up to Hiroshima and Nagasaki, most of whom were civilians.
We use the Axis powers of WWII as a visual shortcut for evil. We depict them as cartoonist, mustache twirling villains who kick puppies for fun.
And at first glance you might think that this is a bit unfair. An exaggeration made by the winners of the conflict against the losers.

But you have to understand, they were worse. In real life they were an evil almost beyond our comprehension. An evil that has to be censored in media because the truth is so extreme that few can believe it.
But it is the truth.
How many American war movies have you watched that included this scene?
“Few know that soldiers impaled babies on bayonets and tossed them still alive into pots of boiling water…They gang-raped women from the ages of twelve to eighty and then killed them when they could no longer satisfy sexual requirements. I beheaded people, starved them to death, burned them, and buried them alive, over two hundred in all. It is terrible that I could turn into an animal and do these things. There are really no words to explain what I was doing. I was truly a devil.”
—Hakudo Nagatomi, testimony recorded in The Rape of Nanking
Yes, that is a real thing that happened. But when has it ever been depicted in any war film? Never, to my knowledge. I doubt even the most somber documentary would put on a dramatization of that.
No, the Japanese were not as cruel in real life as depicted in American war films. They were so much worse.
You couldn’t make a film that accurately depicted the true scale of the cruelty of Imperial Japan. It would go beyond an NC-17 rating. No Hollywood producer would touch it. No theater would show it. American war films have, if anything, sanitized Imperial Japan.
Now, none of that is to say that all Japanese in the 1940s were bad people. Or that any Japanese person today should feel responsible for atrocities committed by other people, just because they share an ethnicity.
But the fact remains, the Empire of Japan is a top contender for the cruelest regime to ever exist.
n North Africa, Ernie Pyle recounted a story about an American ambulance that got lost in the dark in a firefight. They were stopped by a roadblock. A German roadblock! They were in a panic. But the German MPs walked around the back, opened the doors to make sure they were transporting wounded (and not, say, weapons), then signaled the ambulance to turn around and drive off. (Source: Ernie Pyle columns)
Later, in the dense forests of Europe, a battle raged for three days between Allied and German forces. Wounded men were scattered all over the forest, but couldn’t be reached. The commanders raised a white flag and proposed a half-day truce to retrieve the wounded. So for 12 hours, American and German medics and soldiers picked up wounded of both sides, got them onto stretchers and into ambulances to safety — then resumed fighting. (Source: I forget, but it’s well documented)
Meanwhile, on the other side of the world…
At Guadalcanal, Navy corpsmen — medics — began carrying away wounded during a battle. Japanese snipers shot the medics. Then the snipers crept up on the field hospitals, the big MASH tents. They shot surgeons. The idea was, if the doctors are killed, many wounded GIs would die. The Americans hung sheets around the MASH tents to mask off the snipers. The snipers took it slow, pumping bullets into the tents where they guessed the surgeons might be operating. (Source: Robert Leckie’s “Delivered from Evil”. Leckie was a Marine who fought on Guadalcanal.)
Navy corpsmen had to take off their Red Cross armbands and helmets because they were targets. They dressed like all the other Marines. And carried pistols and rifles. Sometimes medics were tending the wounded and had to fire rifles to keep the Japanese at bay. (Source: Leckie)
And early in the war, when the Japanese soldiers captured some [corrected] Australian Army nurses, they gang-raped them. Raped some to death. Raped others until they went insane. Raped the rest until they were bleeding internally, then drove them into the surf and shot them. (Source: Plenty)
So, yes, the Japanese were just as cruel as the movies portrayed.