It is possible that, having seen many people shot down and killed, Capa felt an intense urge to "get" such a moment. But then he realized the astonishing luck that this required--unless, truly, he was a camera that could take a picture as he saw a thing. So did Capa decide to re-stage what was not an uncommon event? If so, was that cheating? Or are we just very sentimental about the kind of "truth" that photography allegedly leads to?
A painter at the front lines could easily and legitimately paint a picture of a falling soldier. No one would object, if the painting was as strong as Capa's photograph. Nobody would cry deceit. Painting, after all, implies measured decisions regarding subject, size, composition, coloring, and so on. Why must photography be different? Is it so reliant on absolute fidelity to the moment? Or must we admit that, for a moment at least, Capa the journalist had become Capa the painter or Capa the novelist? If so, does that cheat the nature of photography or penetrate deeper than the happy faith in spontaneity? ...
On that day in 1936, I suspect, without knowing how or why, Robert Capa had taken one of the key steps that carried photography from a recording device to an intellectual or imaginative process. It does not seem to me a case of possible cheating so much as a proper appreciation of the nature of the medium. It remains for us to decide how moving, or important, photography can be if we do not trust its record.
It's worth reading the whole piece, which you can find here.