The great bomber pilot Guy Gibson had a black labrador with a racist name. This shouldn’t matter, except Gibson loved the dog, and its name was used as a codeword during the bombing raid which made Gibson famous, upon the Mohne and Eder dams in Germany in May 1943. The 1955 movie The Dam Busters retells the story of the raid in thrilling melodrama, and inevitably includes repeated mentions of the troubling name. Nowadays, when the film is broadcast, it either features a warning about offensive language or is shown in an edited version, with the dog’s name changed to ‘Trigger’.

The raid on the German dams is an old and much loved military episode. In it, a crack team of exhausted airmen are assembled for an almost suicidal operation, using the unlikely technology of bombs which bounce on water, breaching the dams and flooding the Ruhr, which was the heart of German industry. In his new book about the raid and its aftermath, the military historian Max Hastings describes it in slightly Boy’s Own terms:

The bombers attacked Hitler’s dams, flying straight and level at 220 mph, much lower than the treetops and less than a cricket pitch’s length from the lakes below, to unleash revolutionary four-and-a-half ton weapons created by the brilliance and perseverance of Barnes Wallis, a largely self-taught engineer.

That cricket pitch is a nice touch. Who could resist this story?

It is also, of course, a myth. This is not to say that it didn’t happen, but rather that some details have been romanticised and  some, such as the dog’s name, simply left out. With Chastise — which was also the slightly prissy codename for the operation — Hastings wishes to give a full and rounded reckoning. Despite its occasional purple flourishes (and, again, who could resist?), the story he tells is a remarkably unsentimental and often technical one.

On the night of 16/17 May 1943, 19 Lancaster bombers flew from Scampton in Lincolnshire to north-western Germany. Each carried a 60-inch cylindrical depth charge encased in wood, and a launch mechanism specially modified to put backspin on the falling bomb. They struck the Mohne first. Four bombs failed to breach the dam, but the fifth succeeded, and the bombers moved on to the Eder, which the third bomb breached. An attack on the Sorpe dam, failed, and eight Lancasters were lost.

Perhaps Hastings’s most striking argument is that the raid was largely pointless. By the spring of 1943, there was a widespread feeling that the British had contributed little to the war against the Germans, and here was the opportunity to show the Americans and Russians that this was also a British war. The dams raid was, he suggests, a PR exercise — and in retrospect it often looks amateurish. The Eder was not even connected to the Ruhr water system, and seems to have been chosen as a target only because it was vulnerable. At the pre-raid briefing, the airmen were shown tourist postcards of it. The detail is both amusing and horrific.

Less amusing is that perhaps 1,400 people were killed by the floodwaters from the Mohne and Eder reservoirs, and most of these were neither soldiers nor even Germans but eastern European women enslaved by the Nazis. Accounts of the operation often stop with the raid itself, but the greatest value of Hastings’s book is that he follows the story into its sad aftermath. Repairs on the Mohne began soon after the raids and the dam was sealed up within 18 weeks. ‘Chastise was a supreme piece of theatre,’ writes Hastings, ‘and in May 1943 theatre was precious to the British war effort.’ This is perhaps too coy. We might instead see it all as, in the phrase of one early critic of the plan, ‘dams nonsense’.

In truth, not much of this is new, and there is a tiredness to the writing. Even Hastings himself has told much of this story before, in his earlier book Bomber Command (1979). He relies heavily on the official narratives of the air war and published oral histories. But what is at stake in this revision of the old glorious narrative is something important. The debate over whether this particular raid mattered is, in miniature, the wider historiographical debate over the morals and efficacy of the whole bombing war.

This in turn is the backdrop to the great ethical and legal debates about warfare today: about the relation between technology and human heroism, about collateral damage and proportional loss, and the role of publicity stunts in terror war. The dams raid was a romantic episode as well as, in Hastings’s telling, a slightly grubbier affair. But perhaps more than either of these it is a powerful parable which might instruct us in our own confused times.