About half an hour into Hara Kazuo's infamous documentary The Emperor's Naked Army Marches On (Yuki yukite shingun, 1987), World War II veteran turned political dissident Okuzaki Kenzō, with Hara and his film crew in tow – or perhaps it's the other way around – arrive unannounced at the home of another veteran. Okuzaki has begun crisscrossing Japan to track down fellow survivors from the 36th Engineering Corps, a 1000-strong regiment stationed in New Guinea during the Pacific War from which only thirty returned alive. His goal: to confirm rumours of an illegal execution committed by members of the regiment against two of its low-ranking soldiers, weeks after Japan had surrendered.

When they arrive at Seo Yukio's home, camera and sound already rolling, the ex-sergeant is seated on the floor in the living room. An invitation inside isn't forthcoming so Okuzaki remains standing outside and begins questioning him through the open door. Like most of the other veterans who are interrogated by Okuzaki in the film, Seo refuses to answer directly the questions thrown at him. After several deflections, he remarks calmly: "We were in a jungle and we could have died any day. I can't really tell you everything that happened." He glances down at his watch and claims he needs to be elsewhere. Then, a surprising thing happens.

As Seo stands up in medium close-up, the image switches to slow-motion. "I was a member of the 36th Regiment," Okuzaki declares offscreen. Hara jump-cuts to a wide shot of Okuzaki, who is suddenly standing inside the house and grappling with Seo. The soundtrack seems to lag a few seconds behind the violence beginning to take shape on screen: Okuzaki's voice as he loses patience ("I'm talking to you. Come here! Answer me!") is followed by some indistinct grunts and rustles as he lunges at the veteran. The film reverts to regular speed, and the sound and image become synchronised again, at the moment where the two men collapse onto the floor. After a brief struggle, Okuzaki ends up straddling Seo, punching him. Seo's wife runs in and pleads with Okuzaki to stop, and the police are called (at Okuzaki's insistence, such is his unwavering belief that his methods and intentions are noble).

Hara remains outside throughout the entire scene, filming voyeuristically through the open door, unwilling or unable to breach the physical and social barrier that his protagonist has just breached. Eventually, some neighbours arrive and subdue Okuzaki, pinning him to the floor. The agitated Seo sneaks in a few punches of his own. "Stop it!" Okuzaki shouts – not at Seo or the men restraining him, but at the camera. "I said, stop filming! I'm getting beat up."

"Stop filming!"

It's ironic that these words are uttered by the instigator of violence and only after the tables are turned against him. But they could just as well belong on the lips of any viewer sitting through this uncomfortable scene, one which would make an exemplary case study on documentary ethics. When should a filmmaker stop filming and intervene? (In a later scene when Okuzaki again assaults a veteran in his home, the man's wife poses this question directly to Hara.) Did Hara show the incident as it really occurred? (What did the jump-cut elide or conceal? And what to make of the crude slow-motion cinematography, an odd stylistic flourish in a film virtually devoid of them?) Perhaps the incident occurred precisely because the filmmaker was present? (Does Okuzaki plead for Hara to stop filming because his performance didn't go according to plan?)

According to Hara's account of this scene, the violence erupted when he switched the camera off momentarily to change the shot.1 This would explain the temporary disconnection between image and sound, the visual ellipsis, and the use of slow-motion to extend the footage so that the audio could catch up with it (the sound continued recording while the camera was off). It may simply be the case that the moment was so spontaneous, so unexpected, that Hara was unable to capture it clearly and in its entirety. Regardless, what resulted on screen remains a bold and violent punctuation mark in both its content and style – a moment which sets a radical precedent in Okuzaki's interrogative methods for the rest of the film, and in Hara's willingness to continue filming them.

It would be simple to dismiss this scene as an unequivocal moral and ethical violation if not for the fact that Okuzaki eventually yields some staggering confessions. After his aggressive, sometimes physical coercion, most of the veterans end up alluding to the truth of what occurred in New Guinea. Some admit their guilt outright, offering a full and honest account of events for what is presumably the first time. By the end of the film, the viewer is left with enough anecdotal evidence to conclude that an illegal execution did take place – and moreover, that the two soldiers were executed under trumped-up charges of desertion so that they could be cannibalised by their superiors. During a subsequent (and much more cordial) visit to Seo, he too confesses to being present at the execution and being one of the soldiers who pulled the trigger.

The scene is the first strong expression of the film's many transgressions: its flouting of conventional documentary practice and ethics;2 its blatant trespasses into private spaces (Michael Moore claims the film as a major inspiration for his own filmmaking3); and its attack, through Okuzaki's relentless interrogation and Hara's equally relentless filming style, on the indirectness and ambiguities particular to Japanese language, customs, and culture, which have prevented or shielded many from speaking openly about the war experience.

Does the end justify the means? People are ambushed, interrogated, verbally abused and even assaulted, by a fanatical Okuzaki whose own sanity is frequently called into question. Yet it is possible that what is exposed is far more violent and horrific, and arguably more important, than the indignities and injuries that the men may have suffered during the making of the film. It is the historical and cultural significance of the veterans' confessions and what they reveal – of the true horrors of war, of lingering wartime values, and of a postwar Japanese society which to this day grapples with issues of war responsibility – that Hara's film challenges us to weigh up alongside the often dubious methods that are employed.

It begins with a scrappy, murky shot of two men grappling and falling to the floor: a disturbing and pivotal moment in the film, as it is in the history of Japanese cinema.