What I've noticed in Vinland saga (and haven't seen as often in other manga) is the way Yukimura sensei employs the conversation between the marching soldiers to enrichen our understanding of the time period, convey the mood of the story and emotion of its characters and the feeling of time passing.
We get to understand things from their point of view, learning about their daily lives, opinions and traditions etc..
That way he adds a human element or you could say through this he lends more realism to his characters in their respective world.
Some details might also be foreshadowing to future events or different cultures & ideals that will play a role in the manga.