Final answer:
Peeta explains that Haymitch won the Hunger Games by using the arena's force field to his advantage, deflecting an opponent's attack back at them to claim victory.
Step-by-step explanation:
According to Peeta, Haymitch won the Hunger Games several years ago by utilizing a strategy that capitalized on the fact that the arena had a force field surrounding it. Haymitch discovered that the force field could deflect objects, and in a clever move during his final battle, he dodged an opponent's weapon and used the force field to rebound it back towards his attacker, securing his victory. This strategy combined with his ability to stay alive by outsmarting the other tributes and making alliances where necessary were key to his success.