The Dambusters raid was an extraordinary act of bravery and a remarkable technical achievement for its time. The military usefulness of the raid was probably limited, but the propaganda value was immense.
The casualty rate was high, even by the standards of RAF Bomber Command. 53 of the 133 aircrew who participated in the attack were killed, a casualty rate of almost 40%.
During the Second World War, the casualty rate on individual RAF bombing raids was usually no more than 5% but the overall casualty rate was still very high. Wikipedia’s page on Bomber Command records:
Bomber Command crews also suffered an extremely high casualty rate: 55,573 killed out of a total of 125,000 aircrew (a 44.4% death rate), a further 8,403 were wounded in action and 9,838 became prisoners of war. This covered all Bomber Command operations including tactical support for ground operations and mining of sea lanes. A Bomber Command crew member had a worse chance of survival than an infantry officer in World War I.Only 27% of all bomber aircrew who served during the war avoided death, injury or capture. The Wikipedia page adds:
Statistically there was little prospect of surviving a tour of 30 operations and by 1943 the odds against survival were pretty grim with only one in six expected to survive their first tour, while a slim one in forty would survive their second tour.Pupils at my school in Lincoln had a sobering reminder of this. In the entrance hall was a glass case containing a book of remembrance to all the old boys who had died in the two world wars. Each day, the book would be opened to a different page, displaying portrait photos and brief descriptions of two of the dead. The casualties of the First World War were mostly infantry. Those of the Second World War were mostly bomber aircrew.
The controversy over the RAF’s area bombing campaign meant that wartime bomber aircrew were never issued with a campaign medal and had no memorial (apart from the Airmen’s Chapel in Lincoln Cathedral) until one was unveiled in London last year.
With perfect hindsight, it is possible to question the efficacy and ethics of the bombing. At the time, Britain faced an existential threat from the Nazis and did what seemed best to defend itself, when the final outcome of the war was by no means certain. It is right that we remember the self-sacrifice of people who put their lives on the line for the rest of us. In the case of RAF bomber aircrew, that means people who were effectively on a suicide mission and knew it.