About the Post-War Arc
The Post-War Arc, also referred to as the Post-Marineford Arc, is the 23rd story arc of the manga and anime One Piece, both the fifth and last story arc of the Summit War Saga, and the last story arc of the first half of the series.
The effects of the Summit War of Marineford ripple across the world for both Pirates and Marines. As Luffy mourns Ace's death, he remembers the childhood he spent with Ace and another brother, Sabo. After coming to terms with Ace's death, Luffy and Rayleigh must formulate a plan for the Straw Hat Pirates to survive in the New World.
All across the world, civilians rejoice that the Marines emerged victorious in the Summit War of Marineford. The Eleven Supernovas, having all assembled at Marineford to take part in the battle (viewing it from a safe distance), realize that Whitebeard has been killed, and all of them take their own separate actions. Eustass Kid claims that the Emperor's death (now consisting of only Shanks, Kaidou, and Big Mom) has caused the balance of the Three Great Powers to crumble, and the world is about to enter an age like nothing ever seen before.
The world reacts in different ways to Whitebeard's death. Pirates celebrate that Whitebeard's claimed that the One Piece definitely exists. Civilians and Marines cheer that Whitebeard is dead. A band of ferocious pirates, under the helm of the self-proclaimed "Brownbeard", attacks the town of Foodvalten, which was formerly protected by Whitebeard. Even though the Marines were triumphant, their victory has inevitably brought nothing but chaos.