Israel's military conscription and precarious existence ensure that citizens who would never be anywhere near uniforms or guns if they lived in another country can find themselves at the sharp end of modern warfare.

Whatever that means for the country's military - and Lebanon hints that a budding filmmaker is not necessarily who you want next to you in combat - it does mean that Israeli artists of all kinds are exposed to experiences that are rarely presented their equivalents in other countries.

It also means that a certain amount of technical verisimilitude is guaranteed in the fine, bleak films made by Israelis about war. However, it may not necessarily guarantee that the films are accurate or representative of the combat experience of the average reservist. Indeed, if you were to judge the Israeli army by its bleak depiction in films like Lebanon, Waltz with Bashir, Beaufort and Amos Gitai's Kippur, you would have to conclude that the Arab enemy must really be useless to be defeated by soldiers as badly led, badly trained, poorly disciplined as the reservists of the IDF.

Samuel Maoz's extraordinary Lebanon, which won the Golden Lion at last year's Venice Film Festival, is based on his own experiences as a tank gunner in the 1982 invasion of Lebanon. In a unique and brilliant innovation that may change the way war films are made, all the action takes place entirely inside a tank. Things that happen outside the vehicle are seen through the lens of the gunners' periscope which becomes literally and symbolically cracked during the course of the film. Those images are sometimes horrifying, sometimes strangely beautiful, with the silhouetted movements of soldiers under fire taking on an almost balletic quality.

The four-man crew of the creaky, old Patton tank are young and inexperienced. There is a driver, a gunner, a loader and a commander, whose authority seems flimsy at best. As their faces become covered with grease and smoke in the wet, claustrophobic interior of the vehicle - which increasingly seems like the belly of a strange green beast - it gets harder to tell them apart.

It is not clear where they are in Lebanon but their mission is to support 12 paratroopers. Very quickly they experience the deadly confusion of irregular warfare, having to decide whether or not to fire on approaching vehicles. Shmulik (Yoav Donat), the gunner, sees through his glass the horrific destruction physical and psychological that has been wrought by bombs and guns even before he and his unit come into contact. He and the other three men never leave the vehicle though they are joined at times by the paratroop commander, a Syrian POW and an Israeli corpse.

In the tight, dark space of the tank, there are necessarily many TV-style close-ups. But Maoz uses them with great virtuosity to envelop you in the increasingly surreal and disturbing world of the four young men. The shots of eyes widening, tearing up or going blank somehow underline the semi-blindness of the unit as it lurches around the terrain.

Even more than in Waltz with Bashir, the combat takes place without a context. There is no mention at all of the PLO, which then controlled parts of Lebanon and was the reason for Israel's invasion. You certainly get no sense of the welcome that was initially given to the IDF by Shiite Muslims who had chafed under PLO rule. It is almost as if the filmmakers are remembering the complex 1982 conflict through the simpler lens of the 2006 war.

The soldiers in the tank have vaguely heard of the Phalange but have no idea why they encounter some Syrian troops (who at times were also fighting the PLO in Lebanon). Indeed, they seem to have no idea who they are fighting or why.

It is as if Maoz would have us believe that young Israeli reservists in 1982 did not read newspapers or watch television. But then there are several times during the film that the four men in the tank seem slightly retarded, as if the unit had been recruited from a special-needs school. (Maoz's alter ego Shmulik in particular behaves in a frustratingly, dumb and passive way, leading to the deaths of both Israelis and Lebanese civilians.)

I wondered if Maoz was trying to illustrate the intellect-killing effect of post-traumatic stress, though these men seem to have PTS even before they have experienced combat.

But then Lebanon is only a realist film on the surface. This is not just because the film's tank is much roomier and less noisy than the real thing, but because Maoz's true aim is presumably to give the audience a sense of the dehumanizing psychological experience that he and other men endured. As with Waltz with Bashir, the film may represent not what happened but how a guilt-ridden and traumatised mind remembers it.

And although the paratroopers are not shown behaving any worse than other nations' soldiers in similar situations, prospective viewers should be aware that the film includes some very upsetting but all-too believable sequences. And though you could imagine the film gratifying anti-Israel audiences, it is hard to imagine any other country portraying its own soldiers at war in such an unsparing way.