This is a 1954 B&W movie based on a 1951 book by Paul Brickhill. Both the book and the movie are excellent.
This film is packed with action, and the tension is maintained throughout. There is not a dull moment. There is a great deal of atmosphere in every major scene. The actors are good and the production is quite realistic. Some of the special effects are not very well executed though. I am sure they could have done better, even with the technological limitations of the early fifties.
Speaking of technology, the first part of this movie deals with the challenge of destroying a dam that is 120 feet thick at the base. We spend a long time witnessing the development of an audacious idea concocted by a scientist who has to go through various trials and tribulations before his concept is vindicated. So the first half of the movie would qualify as a documentary in that regard. But there is just as much action and tension here as there are in the bombing scenes that follow. For the whole story is threaded with the same fabric.
So the second half of the movie deals with the actual bombing of three German dams in the Rhur Valley. That is what we had been waiting for and it is delivered like an apotheoses. Indeed it is the climax of the movie, but the tension is only released after numerous attempts. There is a "feel good" part here, but the triumph is somewhat mitigated by the heavy casualties. That is what makes it a great war movie.