[Warning: The following contains spoilers for Tuesday's episode of This Is Us, "Vietnam." Read at your own risk!]

Tuesday's episode of This Is Us gave the first glimpses of Jack (Milo Ventimiglia) and Nicky's (Michael Angarano) time in Vietnam, and we can already tell the brothers had varied experiences during the war. The primary focus of the episode, also titled "Vietnam," was to introduce how the boys grew up together and yet became completely different Pearsons.

The episode began with Jack traveling to find his brother at another camp in Vietnam not far from where his own troop is stationed. It then rolls backwards through Jack's time in the country so far: enlisting after Nicky got drafted and then back to Nicky's birth before the show returned to their reunion in Vietnam. When Jack shows up at camp, where Nicky does chores after being slapped with an Article 15 for reckless endangerment, the younger Pearson looked puzzled and a bit pissed off to see his older brother standing in front of him.

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"It's complicated," Angarano told TV Guide after a press screening of the episode. "Yeah, it's his brother, but that means a lot of different things for Nicky. Jack, while he's very kind, is also very forthcoming and earnest and protective of Nicky...It's a codependent relationship. And I think part of Nicky's decision to not cross the border and to go to Vietnam in the first place — his dynamic with Jack has something to do with it...Jack coming to Vietnam for Nicky I think is a complicated thing for [him]. You'll see it pretty immediately."

Even though Jack's intentions are simple — protect his brother — their shared life experience and the chaos of war will put the two siblings at odds as This Is Us continues through the Vietnam storyline this season.

Milo Ventimiglia, <em>This Is Us</em>Milo Ventimiglia, This Is Us

"All these brothers had were one another," Ventimiglia told TV Guide. "When you get to adding the complication of war and the horrific nature of war, you've got these two people that just want to be together — these two brothers that just want to be together, but it's not that simple. War is never that simple. I think what we're gonna see is these two men and their desire to try and stay together, even though there are many things getting in the way of that."

The brutal realities of war, and dealing with the atrocities they've both seen, exacerbates the differences between the brothers. So they won't just physically be torn apart, but they'll also away drift away from one another as mental wounds exacerbate the longer the war progresses.

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Nicky resents Jack's overprotection, Angarano said. "I think part of him needs it also, and part of him wants to shed it. But part of what is so complicated and beautiful about this story line is that this dynamic of brothers is very nuanced and detailed. It's a long history between the two of them." The most compelling piece of the story, for him, is how "two people who came from the same place, grew up the same way, now as men at war reacting very, very differently, actually in stark contrast." Jack, naturally, is an outstanding soldier but Nicky's Article 15, is essentially one step above dishonorable discharge. "Nicky's not a good soldier," Angarano said, "and I don't think he cares to be."

While war might bring out Nicky's most destructive habits, it'll help shape Jack into the caring father and husband we've grown to love over the past two seasons.

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"War itself adds another dimension to a person...There's the threat of life and death," Ventimiglia explained. "The Vietnam War storyline that we're playing feels like an elongated version of the house fire where it's there's the very real threat of war and the experience of war that will challenge a person morally, fundamentally, everything about it...Jack's time in Vietnam has definitely reaffirmed this feeling I get from Jack that he cares deeply about people. Even in the throes of war, he's a deeply caring man."

"Vietnam" is just the beginning of a multi-episode arc that will play throughout Season 3 of This Is Us, as we dig deeper in to Jack's time there, and inevitably reach the story of Nicky's death. The actors and crew have traveled to Vietnam to film scenes to come later in the season that add realism and to the story.

"It's going to bring a visual quality that shooting in southern California won't quite have," Ventimiglia said of the trip. "At the same time, I think always just being boots on the ground, so to say, in a place where history happened, it always informs the work."

Fans will have to wait a little bit longer to see that work though. This Is Us creator Dan Fogelman teased that there are episodes without the Vietnam storyline that will arrive before the show resumes with Jack and Nicky, so hold tight.

This Is Us continues Tuesdays at 9/8c on NBC.