With over a thousand chapters to its name, One Piece is one of the longest-running manga series. Eiichiro Oda has created a masterpiece with no glaring flaws, which is why it is the best-selling manga series of all time. While world-building and the overall story are the more important parts of the manga, there is no shortage of action in the series.
In fact, the manga consists of multiple wars that have caused mayhem. These wars were waged for various reasons, but the outcome was the same: destruction. With that in mind, here are the biggest wars in One Piece.
7 Edd War
The Edd War took place 27 years prior to the beginning of the story. It involved the Roger Pirates and Shiki's pirate armada. Shiki approached Roger and tried to become allies. Shiki had learned that Roger had information about an Ancient Weapon. He believed that his armada, along with the Ancient Weapon, would enable them to take over the world.
Roger turned down the offer because he had no interest in such a thing. Shiki felt disrespected, and it led to a massive war on the sea. Despite being at a disadvantage, Roger refused to back down. Fortune seemed to favor Roger as the turbulent weather took out most of Shiki's fleet. The former Rocks pirate could not recover from this incident and eventually faded into oblivion.
6 Wano Country War
The land of Wano served as the battleground for one of the biggest wars that the series has witnessed to date. The Straw Hats entered into an alliance with Trafalgar Law on Punk Hazard. The alliance's aim was to take down Kaido and the Beasts Pirates. As the story progressed, the two pirate crews were joined by other groups that shared the same goal.
The war started with the alliance's raid on Onigashima. There were many big-name pirates on display, which made all the fights exciting. The alliance had to win at all costs, as failure meant that Wano would remain under Kaido's tyranny. Despite being outnumbered, the Straw Hats and their comrades managed to defeat Kaido's army and Big Mom. With their victory, the land of the samurai could flourish once again.
5 Summit War
The Summit War, or Paramount War, started after the Marines decided to execute Portgas D. Ace. They knew Whitebeard would not let them execute one of his sons. So they waited in Marineford for Whitebeard to appear. The Marines were confident that they could complete the execution without any problems.
But they couldn't have been more wrong, as Whitebeard and his allies nearly destroyed the entire island of Marineford. There were casualties on both sides, but the pirates suffered bigger losses as Ace and Whitebeard both died. The deaths of the two notable pirates meant that the Marines were victorious.
4 20 Countries vs The Great Kingdom
Over 800 years ago, twenty nations banded together to fight a common enemy—the Great Kingdom. They believed that the kingdom was a threat to their survival and had to be eliminated at all costs. The alliance of the twenty rulers was successful in their quest and erased the Great Kingdom from existence.
The real reason behind the war remains unknown, but it is possible that the monarchs were manipulated by Imu. As the story enters the final saga, Oda will surely lift the curtains on this secret.
3 Payback War
The Payback War took place between the Blackbeard Pirates and the remnants of the Whitebeard Pirates. Following the conclusion of the Summit War, the Whitebeard Pirates regrouped in the New World. The loss of Whitebeard and Ace weighed heavy on their minds, and to make matters worse, the Blackbeard Pirates hounded them.
The Whitebeard Pirates had no other option but to defend their honor. Unfortunately, the Blackbeard Pirates overwhelmed their adversaries, resulting in Blackbeard becoming one of the Yonko. It is unclear if the Whitebeard Pirates suffered any more casualties, but given the malevolent nature of their enemies, it would be unwise to rule out the possibility.
2 God Valley
While it has not been labeled as a war, it did have the same magnitude as one. The incident took place in God Valley after the Rocks Pirates attacked the Celestial Dragons. This forced the Marines to take action, and they sent Garp to the island. Before engaging the Rocks Pirates, Garp ended up forming an alliance with Gol D. Roger. The Marines and the Roger Pirates clashed with the Rocks Pirates and defeated them.
The Rocks Pirates disbanded, and their captain was never seen again. Following the incident, Garp earned the epithet "Hero of the Marines," while Roger went on to become the King of Pirates. Also, God Valley mysteriously disappeared from the world map.
1 Alabasta War
The Alabasta arc was focused on the Straw Hats' battle against the Baroque Works. The organization led by Crocodile sowed the seeds of discontent among the people of Alabasta. The citizens were fed lies about how the royal family was behind the lack of rainfall.
This caused the civilians to take up arms and rebel against Nefertari Cobra. If the Straw Hats had not stopped Crocodile and his henchmen, Alabasta would have been covered in the blood of hundreds of innocent people.