On the night of 16–17 May 1943 a squadron of RAF bombers, led by Wing Commander Guy Gibson, attacked a number of dams in the Ruhr industrial heartland of Germany. Operation Chastise used ‘bouncing bombs’ conceived by the British engineer Barnes Wallis to evade the dams' defences. Two of those dams – the Möhne and the Eder – were breached, although the Sorpe crucially evaded serious damage. Of the 133 men who set off that night, 53 died and another three were taken prisoner. Meanwhile around 1,300 people were killed by the flood waters. The story of the Dambusters was immortalised in a 1955 film.

Sir Max Hastings is a journalist and historian who served as editor-in-chief of the Daily Telegraph, then editor of the Evening Standard. He has written many bestselling works of military history, among them Vietnam: An Epic History of a Tragic War and All Hell Let Loose: The World at War 1939–1945

Rob Attar: Where did the idea to attack dams originate?

Sir Max Hastings: The RAF figured out back in 1937–38 that if it was possible to destroy the Ruhr industry’s water supplies, it would strike a devastating blow at the heart of Nazi industry. So they knew they wanted to do it but they didn’t know how.

Then a very bright man called Arthur Collins discovered that if you placed it right up against the dam wall, a much smaller charge could break the dam than if you exploded it even 10 or 20 feet away. He thought that about 6,000 or 7,000 pounds of explosive might do the business, and the Avro Lancaster, the new heavy bomber, might be able to carry that. But how did you deliver that charge right up against the dam wall?

Here, Collins’s research married with that of Barnes Wallis, who believed that they could get a big depth charge – which was what it really was, rather than a bomb – and bounce it across the water, over the torpedo nets guarding the dams. And it might then be possible to get a big enough charge to the dam to explode it.

How much of a challenge was it going to be to deliver a ‘bomb’ in that fashion?

I only use the word ‘hero’ very sparingly but I think it’s right to use it of these young aircrew who were recruited to the newly formed 617 Squadron. They were asked to do something very difficult: to drop one of these bouncing bombs from a height of 60 feet – less than the length of a cricket pitch – not in a nimble fighter but in a heavy bomber, while steering straight and level towards the dams and, in the case of the Möhne, with anti-aircraft guns shooting at them. It was a monstrously unfair thing to ask of these guys. Heavy bombers are like people carriers, not Lamborghinis; they’re great, galumphing load carriers.

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What did the raid’s planners hope to achieve?

Both Barnes Wallis and Charles Portal, the head of the RAF, convinced themselves that if they could break the Möhne, this would strike a huge blow against German industry. But actually, the experts at the Ministry of Economic Warfare warned them early in 1942 that the key to the Ruhr water supplies were two dams: the Möhne and the Sorpe. The Sorpe was a great earthen dam and they knew you couldn’t bounce a bomb towards it because it had a sloping face. And also it was such an enormous construction that even Wallis, at his most optimistic, thought that it would take four or five of his bombs to do the business.

They had to face the fact that the most they were going to be able to achieve was to make a hell of a mess in north-west Germany and cause the Germans a lot of embarrassment and inconvenience. But by then the squadron was trained and a huge industrial effort and technological effort had been put into creating these bombs. And they knew that even breaching the Möhne was going to be spectacular.

The key thing is that in 1943 the British people were pretty tired and our reputation in the eyes of the Americans stood pretty low. Everybody could see that the tide of the war was turning, but they could also see that the Russians were doing most of the heavy lifting. Churchill understood the need for what I call military theatre. Even if you couldn’t do big things like launch D-Day, you could at least do things that had a spectacular effect.

Everybody told each other a lot of fibs before the raid but I think if I’d been sitting where Charles Portal was sitting in 1943, desperate for some spectacular successes, then I would have thought that it was a fair gamble. In fact Portal said, in one of his papers before the dams’ raid: “This looks like a good gamble.” And I think it was. But we should never underrate what these kids were being asked to do.

An aerial view of the Mohne dam showing the damage caused by Operation Chastise. The floodwaters killed more than 1,200 people. (Image by Alamy)
An aerial view of the Möhne dam showing the damage caused by Operation Chastise. The floodwaters killed more than 1,200 people. (Image by Alamy)

How did the raid itself go?

It was fantastically dangerous. The only way the crews had a hope of seeing enough to be able to attack the dams was to fly in moonlight, in which Bomber Command never normally operated because the Germans could see you so easily. And they made the calculation that the only way they had a chance of getting there was to fly all the way at deck level. But flying at 60 or 100 feet, you face a big risk of hitting power cables. Meanwhile, the anti-aircraft gunners can hear you coming even before they see you and they’re firing at practically point-blank range. So it is not surprising that three of the 19 aircraft that took off were destroyed by power cables or by a searchlight, while more were shot down by flak.

What is miraculous is that enough got through to be able to break the Möhne and the Eder: it was an extraordinary feat. But it cost eight aircraft lost out of 19, and a couple more that turned back at the beginning. That was nearly a 50 per cent loss rate and everybody knew you couldn’t run an operation like that very often. It’s interesting that, after the raid, when they were recruiting to bring 617 Squadron back up to strength, they had a lot of trouble finding volunteers. Everybody knew that the casualties had been frightful and they thought that, if there are going to be any more operations like this, then this is not a place you want to be.

Because they failed to break the Sorpe, not much is normally made of that part of the raid. But those pilots and their crews, they flew over the Sorpe again and again to figure out how to make an approach that gave them a chance of dropping the bomb. If the Germans had been awake, which amazingly they weren’t, they could have vectored night fighters there. Incredibly they didn’t do it, but the crews had no way of knowing that.

Joe McCarthy, the one American on the trip, only dropped his bomb on the 10th or 11th run. It’s not surprising that one or two in the crew were saying in the intercom: “Can we just get this f-ing bomb out of here?” And what one always has to remember about what makes bomber war unusual is that, unlike being a soldier, you don’t have personal choice as to whether to be brave in battle. If your captain decides to be brave, you’ve got to go with him all the way.

I can’t help suspecting that there must have been more than one member of Guy Gibson’s crew – who astoundingly flew round the Möhne about four or five times – who were thinking: “Well, it’s alright for him if he wants to win a VC but what about us poor bastards?”

What was the impact of the attacks on the people living close to the dams?

When I grew up, one of the things that seemed wonderful about the raid is that it was victimless, apart from the 53 air crew lost. But, of course, somewhere between 1,200 and 1,400 people were drowned – more than half of them slave labourers and prisoners of war. You suddenly had hundreds of millions of tonnes of water being unleashed, pouring down the valley, creating what I call a biblical catastrophe. I’ve devoted a whole chapter to the stories of what happened when this wave of water, 40ft high, came smashing through. You had whole houses being borne down the flood.

If you want to take the ruthless view, you can say this was a price the German people had to pay for Adolf Hitler. They had supported Hitler; they were fighting for Hitler until 1945; and this is the sort of stuff that happens. And plenty of British civilians had been killed: men, women and children.

But it was still a terrifying story and we have to see that side of it. It’s not enough to say: “Whoops, didn’t we do brilliantly well, wasn’t it wonderful, gee whiz.” We have to also say that this inflicted a terrible human disaster, even if this doesn’t negate the courage of the people who took part.

In his memoir, Enemy Coast Ahead, Guy Gibson himself wrote about how uncomfortable he had been when one or two of his crew, on the way home from the raid, were making pretty callous remarks about all those people being drowned. And he wrote: “No one likes mass slaughter and we did not like being the authors of it. Besides, it brought us in line with Himmler and his boys.”

I suspect that one or two of Guy Gibson’s crew were thinking: ‘It’s alright for him if he wants to win a VC but what about us poor bastards?’

How did the raid affect the German war machine?

It had a tremendous shock effect. When Albert Speer, Hitler’s armaments chief, flew over the area at first light he was horrified and thought this was going to be a complete disaster. But he was amazed at how quickly production was restored. The raid made an incredible mess, killed all these wretched people, and was a terrific psychological blow, but its impact on German industry was very limited.

I would still say it was worth it because it gave a huge boost to the morale of the British people and raised the standing of the British in the eyes of the Americans. So while its strategic impact was almost nil, in the grand scheme of things, its propaganda impact was immense.

There was one huge mistake made by Arthur Harris [head of Bomber Command], partly because he had thought the whole thing was ridiculous anyway. Through the summer of 1943, there was a vast edifice of wooden scaffolding up in front of the dams, and Speer was dreading a conventional RAF bombing raid, which only had to be reasonably accurate and this great cat’s cradle would come tumbling down. But the RAF made no attempt to break it down. Speer made plain, if they’d wrecked the repair work then it could have led to serious trouble. As it was, the Möhne and the Eder were both operational by September, when the autumn rains came, and that winter they were doing the business again for German industry.

Back in 1979, I interviewed Barnes Wallis and he said the big mistake was not to have launched a follow-up raid. When I interviewed Sir Arthur Harris, I put this point to him and he said: “Any operation deserving of the Victoria Cross is, by its nature, unfit to be repeated.” Now, he was right that, as the Germans had put up all these balloon cables and flak guns and searchlights, you couldn’t ever do another low-level bouncing bomb raid. But you could have done a conventional raid, and that was a huge error.

How much is our modern view of the raid shaped by the film?

We all think we know the Dambusters story, but most of that is wrong because it’s so much influenced by the movie. And it’s a great movie: it’s the most popular British war movie of all time, and deservedly so. But the portrayal of most of the characters was a lot different from what they were actually like, and the story wasn’t of Barnes Wallis fighting a lone battle against an unthinking bureaucracy. What was really remarkable was that, in the middle of a war of national survival, when resources were very scarce, Britain’s warlords supported this amazing venture.

Listen to Rob Attar’s interview with Sir Max Hastings the History Extra podcast soon.


This article was first published in the October 2019 edition of BBC History Magazine