Is this an example of apposition: "Soldiers, in his day, did what they had to do and didn't speak of it once they came home."?
When you think of apposition, you first want to look at the subject, in this case, soldiers. Then, see if the rest of the sentence sort of defines the subject. This one is tricky because you kind of want to overthink it, but "in his day" is not the defining characteristic of all "soldiers," if that makes any sense.