While season 1 tried to balance out Jack Pearson's (Milo Ventimiglia) flaws, "This Is Us" season 2 seemed dedicated to revealing where those weaknesses came from in the first place. In the episode of the series titled "A Manny-Splendored Thing," fans found out that Jack had been lying about his past.

Over the last year, viewers have seen a glimpse of Jack's past such as meeting his alcoholic father Stanley (Peter Onorati). But the second episode of season 3 gave everyone the most significant peek to the life of the lead character. It showed him haunted by his Vietnam memories, where one of the flashbacks displayed him carrying an M-16.

The episode featured how Jack attempted to fight his vices. While the scene shed light on why the character was battling many demons in his life, mainly the horror of the Vietnam War, it also revealed that the Pearson patriarch had been hiding a major secret about who he was for at least a decade.

In the season 1 finale, Jack helped fix Mrs. Peabody's car and eventually told her that he became a mechanic in Vietnam. This differed from the flashbacks where he was seen in a military uniform, carrying a war-ready assault rifle. In episode 2 of the third installment, viewers witnessed that he was just not a mechanic in Southeast Asia; he clearly fought in the war.

In an interview with Entertainment Weekly, series creator Dan Fogelman revealed that Vietnam would play a big part in the story of Jack in "This Is Us" season 2. He said, "Clearly there's a new piece of the puzzle toward Jack being added on here, which is Vietnam."

He further added, "And the fact that you're flashing to something when he's hitting that punching bag that doesn't quite match up with what he's told his family about his experience in Vietnam is a place that we're certainly going to be exploring not just this season but as the series continues."

The revelation about the past of Jack explained why the character became alcoholic. In the scene showing him beating his vice through boxing, it also displayed how he dealt with the ghost of the Vietnam war, which was precisely the reason why he turned out to be a drunkard.

To know more about Jack and the Pearson family, watch "This Is Us" season 2 every Tuesday, at 9 p.m. ETD on NBC.