Jack Pearson's time in the Vietnam War has, up to this point, been a large mystery to This Is Us fans, but co-showrunner Isaac Aptaker recently confirmed Season 3 will change that. The co-showrunner confirmed the new season will spend "a lot of time" in Vietnam, and fellow showrunner Elizabeth Berger elaborated on what's to come:
There's something very freeing about being past the mystery of Jack's death and moving into this new chapter and being able to tell a completely different kind of story. To be all of a sudden [writing] about the Vietnam War is very special and different.
"Very special" and "different" are great adjectives to describe Jack's upcoming Vietnam storyline, as This Is Us will head into unfamiliar territory in Season 3. The show included a few war props and sets while Kevin was filming his war movie with Sylvester Stallone in Season 2, but Elizabeth Berger's comments make it sound as though the show will be aiming for more than just a few scenes with Jack in Vietnam. Berger mentioned to TVLine the war tale was "the next chapter" of Jack's story following his death, and if this storyline is as long as that one, then the show certainly will be spending a lot of time covering the Vietnam War.
It sounds ambitious for a show that's mainly relied on everyday drama to try and tell a prolonged war story, which may be why stars like Mandy Moore have been using that word to describe Season 3 of This Is Us. The show isn't flying completely blind into the fog of war, however, as the writers' brought on famed war writer Tim O'Brien to serve as a consultant for story arcs that involve Jack's time in Vietnam. O'Brien has written extensively on the Vietnam war, so no doubt he was able to fill whatever holes or clarify any misconceptions the writers may have had, in what could've been the most vital task in Season 3 given a large chunk of Jack's story hinges on it. Kevin will spend some time in Vietnam, likely in connection to his father as well.
This Is Us fans don't know much about Jack's time in Vietnam, but what they do know isn't great. Fans are expecting to see a lot of Jack interacting with his brother Nicky, who we already know will die at some point during the war. It's a very traumatic event that Jack has shielded from his family to the point that he casually recounted it when asked by a young Kevin and Randall. The end of Season 2 showed a flash forward of Kevin headed to Vietnam, and while we're unsure exactly why Kevin is headed to the country, we're guessing he'll find answers that he never got from his father back in the day.