Throughout both installments of The Hunger Games: Mockingjay, it was revealed that Peeta was physically and mentally tortured by the Capitol. They used tracker jacker venom to distort his memories to turn him against Katniss.
Although it is not specified in the text what was the most successful treatment, Primrose Everdeen suggested "reverse hijacking," in which Peeta received a dose of calming morphling and was exposed to happy memories of Katniss.
It took time for Peeta to break out of that conditioning, and even when the possibility existed that Peeta could be a danger to Katniss, the two of them still elected to be together and build a future in a post-Hunger-Games world. Their love for one another is evident.
What happened to Peeta at the end of Catching Fire?
Six tributes in total survive the 75h Annual Hunger Games: Enobaria, Beetee, Finnick, Peeta, Katniss, and Johanna. Katniss, Finnick, and an injured Beetee are rescued by the rebel forces. On the other hand, Enobaria, Johanna, and Peeta are captured by the Capitol and imprisoned.
The Capitol captures and tortures Peeta after Katniss escapes The Quarter Quell, and though he's rescued at the conclusion of The Hunger Games: Mockingjay - Part 1, he's been brainwashed to treat Katniss as an existential threat.
Given that she is willing to make the ultimate sacrifice to protect Peeta, it's safe to assume that the Morphling was committed to the rebel cause. Like the other victors, she knows the power that Katniss has as a lightning rod for the rebellion, and she knows that Katniss will not help without Peeta.
Peeta urges Katniss to run and stays to fight fellow tribute Cato while she escapes. He survives the encounter with Cato but suffers a stab wound on his leg. He camouflages himself into the rocks and mud alongside a riverbank, slowly dying of blood poisoning until Katniss finds him days later.
Gale does not marry anyone in The Hunger Games. He and Katniss talk about running away together and starting a new life in the wilderness, but they never officially marry.
He has betrayed her and is betraying all of District 12 by buddying up with the Careers, whom she calls the "Capitol's lapdogs." She decides that if the Careers don't kill him, she'd be more than happy to. Then, she wonders why Peeta hasn't told them about her bow and arrow skills yet.
Toward the end of the novel, Katniss realizes that Haymitch has been keeping information from her and using her to help the rebellion, causing her to feel extremely betrayed. On the other hand, his goals are generally good ones.
Katniss here's this and understands that even though she may not love Peeta (then) that it's one less person who has to die. (At least that's what I have always thought.) Katniss realizes that if she pretends to be in love with Peeta people will want the capitol to let them survive.
It's only implied that they get it on via snuggling and other affectionate acts in close quarters — but if you have read the book, they really imply that they took their relationship to the next level.
Katniss Fell in Love With Peeta During the Quarter Quell
However, it wasn't until Mockingjay -- when Peeta got kidnapped by the Capitol -- Katniss realized how much she cared about him and that she couldn't live without him.
What does Peeta whisper to Katniss when they reunite?
Then, he opens his eyes. He has camouflaged himself in mud, leaves, and vines. He jokes with her, whispering that it's okay to kiss him since they're madly in love, but once Katniss begins to clean him in the stream, she can see how weak he is.
In Chapter 9, as Caesar Flickerman interviews Peeta before the Games, Peeta reveals to Caesar and all of Panem that he's in love with Katniss. Peeta's revelation sets in motion the storyline of him and Katniss as ill-fated lovers that carries on throughout the Games.
While a prisoner of the Capitol, Peeta was hijacked into believing that Katniss was not human, but in fact one of the Capitol's mutts. Conversely, Johanna Mason suggested that the Capitol's torture replaced Peeta with an "evil-mutt version" of himself. This sentiment was later echoed by Katniss.
Although she will never know for sure, Katniss does recognize that she cannot be with Gale. She will never be able to forgive him for his idea — the parachute bombs — that killed Prim.
Peeta used the dyes to paint a picture of Rue after Katniss covered her with flowers when she died. He says he wants to hold them accountable for killing Rue, and Effie tells him that that kind of thinking is forbidden. Katniss then tells the team she hung a dummy of Seneca Crane.
He says that the rebels and Capitol supporters must not fight, and he asks everyone to lay down their weapons. The interview ends, but not before Katniss realizes that Peeta's support of a cease-fire makes him a traitor of the revolution.
Before the Capitol battle, Gale had explained to Katniss his series of bombs designed to feed off human compassion: a small bomb would go off, and then when medical aid rushed in, a second bomb would go off, killing those people as well. Incidentally, it's this exact type of bomb that took Prim's life.
Katniss's focus on survival and her family's safety prevented her from fully considering romance, but her feelings for Peeta and Gale diverged in the end. Katniss ultimately chose Peeta because he understood her trauma and she didn't want to lose him, proving her love for him.
At the end of Mockingjay, Gale relocates to District 2 and begins working in the district's government. He helps train replacements for the Capitol's Peacekeepers. By this point, he knows that he and Katniss will never be together.
Katniss is rendered deaf in one ear after she blows up the Careers' supplies, and she doesn't regain any hearing on her left side until afterwards when the Capitol gives her a hearing aid.
I'm re-reading the hunger games books in this glorious hg renaissance and I'm trying to figure out in my head how many days passed between cato stabbing peeta in the legs after the tracker jackers and Katniss finding him at the lake.
As she approaches him, Peeta wraps his hands around her neck and throws Katniss around the room. He begins to strangle her, nearly killing her. He is wild, unable to be stopped, at least until Boggs knocks him out with a metal tray.
