The first indicator is the fact that they choose a blood relative of one of the 1,600.
The second indicator is they let him choose a person of equal rank to partner with.
The third indicator is the commissioned officer warning the messenger that he should give his message with more than one as an audience. Because the likelihood of his message being ignored was very high.
Another indicator is the dogfighting that is shown in parts of the film.
This doesn't mean there aren't any holes in the story. There definitely are if you want to pick it apart, but they did a good job of providing enough context to justify the story. It's more a story about people, than war itself.
