I wouldn't say this is an anti war film. The mission was seen as a good thing. All the enemy deaths are dehumanized. It is a good film but it is more of pro-war adventure film. A real anti-war tries to show how every war is a bad idea and every murder on the battle field is a tragedy. Some good anti war films are Apocalypse Now, The Paths of Glory, Full Metal Jacket and etc. By the way, Saving Private Ryan is not an anti war film for similar reasons.
Oh, do I agree.
I'd also add that the original story "The Guns of Navarone" was written by Scottish novelist Alistair Maclean. Who served in the Royal Navy during World War II both in the Atlantic, in the Med, and in the Pacific. And while he was never wounded in combat, he was believed to have been injured in a gunnery training accident on board his ship. But no doubt, he saw men die, both friends and foes, so he was well aware of what it was like to take a human life, which may be why the book is far less violent than the film version.
Some of his other books that take place during World War II. And there be spoliers ahead.
"Force 10 from Navarrone"
The sequel to the original, which was also made into a film with the same title. One of his few novels I have not read, but having seen the film version, it is a much lesser film than the original film.
"Where Eagles Dare"
Again made into a film, which again is much more violent than the novel. Indeed, if I can remember the novel correctly, it is one of the few novels set in Europe during World War II in which not one German character dies. Again, indeed, one of the heroes actually risks his life to save one of the German soldiers in the castle, when a fire breaks out in the castle.
"South by Java Head"
Where the German villain comes off much better than the Japanese in the book, and actually risks his life to save the English characters who are held by the Japanese and are about to be killed by them. And as far as I know never made into a film.
His debut novel and based somewhat on his experiences, while he was in the Royal Navy. And I have it as being one of the greatest novels ever written about warfare at sea and with a rousing ending. Where nearly every character in the book dies, and at the end, the ship, which is out of ammo, is reduced to firing illumination shells at the enemy, but still attacks a superior German ship, before it is sunk. Again, unfortunately, never made into a film.