When you deal with many soldiers and other personnel that was involved in one (or many) of global (or regional) events, I would rather pick from a list of of such events.
I like the historic events, but I need to indicate that this person took part in it somehow as an occupation. Saying that he was a US soldier at the time is not enough because not every US soldier was deployed to every event.
Yes if you create shared notes, e.g. "WW I" or "Vietnam War", you can add these notes to all soldiers who were involved in these wars. When you then navigate to the shared note, you can see a list of all involved persons in these wars.