Clint Eastwood may have made more impressive films than this portrayal of the Japanese defence of Iwo Jima, told in their own language. But he has surely never made a braver one.

It's doubtful whether Hollywood would have allowed a film with subtitles from anyone else but the veteran Oscar-winning star and director.

Shot back to back with Flags of Our Fathers, which relates the same battle from the Americans' point of view, the second part of Eastwood's double-header doesn't defend the Japanese as paragons of nobility.

It does attempt to explain that wars have their heroes on both sides and that armed conflict often murders the souls as well as the bodies of those who have to fight them.

The fierce battle for the inhospitable volcanic island of Iwo Jima, vital for any future invasion of Japan and considered by the Japanese to be part of Tokyo (even though the city is 700 miles away) resulted in the death of 7,000 American troops, with another 20,000 wounded.

Only 1,000 of the 20,000 Japanese defenders survived. This, unusually for Hollywood, is the story of a heroic but crushing defeat, partly gathered from the buried letters found years later on the island.

The Japanese were short of men, ammunition, communications equipment, food and water. They had no air cover and an appeal for reinforcements was rejected by the mainland as impossible. Since surrender was unthinkable, death or suicide were the only eventual alternatives.

Eastwood, shooting in what looks almost like black and white, possibly for the purposes of realism and to give a documentary feel, begins in late 1944 with the arrival of General Kuribayashi (Ken Watanabe).

Controversially, he moved his artillery from the beaches to high ground and built a series of connecting tunnels and caves covering 18 miles, in which his troops could shelter from the constant bombing from the Naval Air Corps and the shelling from the huge American fleet, which lay out at sea.

Watanabe, the only professional actor Eastwood uses, portrays Kuribayashi as an honourable soldier who knows he will die and worries about leaving his wife without having laid the new kitchen floor he promised her.

Thought by some to be a weak man and pro-American, since he had travelled there and initially opposed the war, he comes to realise that most of his troops will fight to the death, despite their doubts about his strategy.

The other leading character is an ordinary soldier, played by pop star Kazunari Ninomiya, a baker who just wants to get home to his wife and newborn daughter.

The film hinges on the contrast between these two. Eastwood spares us little blood and gore but concentrates as much on the psychological as the physical.

The difference in the cultures of Americans and Japanese is underlined throughout, but the central idea is that soldiers are soldiers and that war is hell.

We should know that by now. But we are still puzzled by misconceptions about the Japanese, their sense of honour and their fanatical capacity either to die willingly for their country or to commit suicide.

Letters from Iwo Jima walks a thin line between factual events, political sensitivity and fictional drama and there are times when a difficult balancing act seems just that.

However, it has clearly been well-researched and filmed with considerable skill, mostly in Iceland rather than on Iwo Jima itself.

The whole is a more satisfactory entity than Flags of Our Fathers - and the final scene, which has veterans and relatives scouring the tunnels and caves for the buried letters, is a suitably moving coda.