Few film critics are war veterans – I count it a personal blessing – but we are nearly all war movie veterans, so many of them do we sit through.

Perhaps there is something obscene about how jaded you get, but eventually you stop cowering beneath the onslaught up on screen and suppress a yawn as another missile turns a building to rubble, another bullet-wound fountains with blood. "Desensitised" is the word. Yet I don't think anyone will be blasé after watching Waltz With Bashir, Ari Folman's beautiful and horrifying account of the first Lebanon War of 1982 as experienced by his younger self.

It's not only the film's animated format that sets it apart, though the graphic precision is a key to its originality. Waltz With Bashir is a lesson in the persistence of memory, a particular memory Folman believed he had lost but was actually lying in wait, like a corpse in a frozen pond. The unwitting trigger is an ex-army friend's story of his recurring dream, in which he is chased along a street by a pack of vicious dogs, all yellow eyes and slavering jaws. Folman perceives this to be a nightmare of war, yet wonders why he, who also fought in the war, has no recall of it. "Was I there?" he asks himself. On that issue alone his film provides an unequivocal answer. He proceeds to track down the soldiers he fought alongside as a 19-year-old Israeli conscript, and slowly, painfully, he reconstructs a mosaic of those days in the eye of the storm.

What keeps replaying in his head is a nocturnal image of himself and his comrades rising out of the sea, in front of them the city of Beirut lit by the sulphurous glow of rocket flares. There's an air of indefinable menace, but the exact meaning of the image isn't clear. It chimes with the hallucinatory experience of the conflict itself – of terrified young men firing into the dark, of tanks rolling through a shattered necropolis, of a gun battle fought against snipers hidden in highrise windows, and the sight of a soldier dodging the fire, waltz-like, in front of a gigantic poster of Bashir Gemayel, the Christian Phalangist leader.

Gemayel's assassination just days before was the infamous catalyst for Phalangist militia to enter two Palestinian refugee camps and slaughter hundreds, possibly thousands, of men, women and children. And here's the moral crux: Beirut was under Israeli control, yet no attempt was made to stop the massacre. Interviews with TV journalists and soldiers (mostly voicing their own digitised talking heads) stop short of laying blame on the Israeli government, and a very large question goes begging.

Waltz With Bashir presents its audience with a serious challenge of interpretation. Folman stresses the slippery, unreliable nature of memory, but is that actually a way of ducking his own responsibility? I began thinking it was, and for a long stretch of this film one detects more sympathy for the traumatised Israeli soldiers than for the massacred civilians of the Sabra and Shatila camps. But then one thinks again of those ferocious slavering dogs at the beginning: does the image signify a confession of complicity? And when, in the very last minutes, the film switches from animation to actual news footage of the Palestinian dead, one wonders why Folman would include such emotive pictures if they weren't somehow prompted by conscience.

Just to complicate the matter, the present Israeli government has embraced Waltz With Bashir, which suggests that Folman has performed a very notable trick. But the most persuasive evidence of Israeli doubt is that the film was made at all – it's a powerfully ambiguous meditation on personal and collective avoidance.