The Fire, by Jörg Friedrich, trans. Allison Brown

One reader of Jörg Friedrich's epic account of the Allied air offensive against Germany during the Second World War told him it was "an encyclopedia of pain". The seemingly endless recapitulation of death and destruction certainly makes it hard going. But Friedrich's method and style are mesmerising. This is a book that demands to be read, no matter how uncomfortable the experience.

But it also calls for caution. The book aroused controversy in Germany because it seemed to draw an equivalence between Nazi genocidal policies and Allied goals in the air war. When Friedrich characterised the bombing campaign as a "comprehensive extermination strategy", he seemed to be evoking the victimhood of the Jews in order to curry sympathy for the Germans.

Allison Brown's fine translation reveals that, while Friedrich may not be entirely acquitted, his thesis is more complex and ambiguous than some of his critics allowed. Friedrich describes the air war as a high-tech duel in which the balance of advantage oscillated. It took the RAF many years to reach the point at which it could gut German cities, and was able to do so with impunity only in the last months of the war. Until then, each raid was a battle in the air rather than a massacre on the ground.

The rate at which lumbering Wellington bombers were shot down meant that the crews were "flying in their coffins". The first daylight raids by the US Army Air Force resulted in slaughter among the bombers. It was no surprise that air crew barely thought about the effects of bombing. Their main concern was staying alive. Nor were the civilians innocent victims of a strategy devised by politicians and generals. The devastating raids on Warsaw, Rotterdam and London were applauded in the German press. When the RAF hit back, it won a chorus of approval. Anyone reading a newspaper in London or Berlin could get a clear idea of the misery that bombing was inflicting.

However, the RAF embarked on area bombing only after years of striking ineffectually at economic and military targets. The initiative came from the Chief of Air Staff Sir Charles Portal rather than "Bomber" Harris, who is usually blamed. Harris certainly believed that the RAF could win the war by levelling 40 German cities, but he discovered that this was not so easy. The RAF ended up targetting medieval city centres because it was easier to identify them (cathedral spires were particularly useful) and they burned well.

Even then, Harris rarely achieved the knock-out blow he aimed for. The RAF "succeeded" in Hamburg in July 1943 because weather and other factors coincided to produce a firestorm. Harris's dream was to repeat the exercise on Berlin and so topple the Third Reich. But Berlin was, literally, made of sterner stuff. It did not burn well. The RAF suffered horrendous losses in pursuit of Harris's elusive apocalypse.

The statistics are surprising. While 1.5 per cent of the German urban population was killed in air raids, over 40 per cent of RAF crew were shot down. German civil defence measures were effective and, until late 1944, the Luftwaffe, in a fearsome combination with anti-aircraft artillery, took such a heavy toll that only one in three RAF airmen had any hope of completing the regulation 30 missions.

The high death toll among the Germans, over 425,000, was not a result of firestorms such as those in Hamburg and Dresden. These were unusual. Rather, it was caused by steady attrition. The bulk of the killing came in 1945 when cities were swollen with refugees and the Allies had air supremacy. Friedrich is scathing about the policy of hitting targets with limited military significance when the war was nearly over.

However, his own evidence is ambiguous. He asks "Did Hildesheim [a pretty city with a medieval core] have to be wiped out because of the train station?" Well, later he explains why the Germans considered that "train stations were the front".

He notes that until autumn 1944, arms production was only slightly reduced by the bombing, but his chapters on air-raid protection and counter measures show how they drained resources from other fronts. Friedrich powerfully demonstrates that bombing failed to destroy civilian morale and actually forced the population closer to a regime skilled at propaganda and welfare measures. But he also observes that, by March 1945, German troops could not see the point of defending rubble, while civilians muttered "The Brits should come and bring this to an end".

At times Friedrich's bias takes over. While he excoriates the British for practising the "politics of annihilation", he claims German bombing campaigns were improvised. By suggesting, on flimsy grounds, that Hitler was lured into a "trap" when he ordered the bombing of London, he implies that the Germans cannot be accused of sowing the wind.

By focusing narrowly on the experience of the bombers and the bombed, Friedrich creates a stupendous memorial to human suffering and cultural loss, but he screens out the wider effects that made them necessary and justifiable. He ignores the likely impact on the land war if resources consumed by air defence had been unleashed against Allied troops and tanks. If civilians died for lack of bunkers, it was because Hitler wanted more pillboxes at the front. The Nazi leadership, not the Allies, decided that mass death was a price they could afford to pay and that a judicious mixture of hand-outs and terror would keep the population in line.

The most heart-rending passages describe the fate of the elderly, women and children. Whereas a soldier could always surrender, they had no choice. But if Hitler had possessed enough steel and concrete he would have protected his people, and confounded the Allies. Ultimately, German suffering was the responsibility of his regime and those who supported it. Friedrich avers that "it is not my profession's to judge who deserved or did not deserve what". But by arguing consistently that Germans did not deserve "the fire", he comes close to excuplating the regime that doomed them.

David Cesarani is research professor in history at Royal Holloway, University of London