The Yonko are the four most notorious and most powerful pirate captains in the world (by the World Government), but are neither allies nor enemies of one another, preferring to remain autonomous under most circumstances. These four individually reside within the second half of the Grand Line (known as the "New World"), exerting impressive influence/control over dozens of other pirate crews and self-governing islands.
In the decisive Battle of Marineford, Whitebeard, one of the Yonko, met his end towards the climax of the Whitebeard War. Blackbeard, his assassin, subsequently usurped his position. Shanks, another member of the Yonko, arbitrated a ceasefire to end the aforementioned war.
As an entity, the Yonko are one of the three great powers of the world, the others being the Shichibukai and Marines. Their strength and influence are such that they live quite literally as though they are emperors, doing mostly as they please. Individually, they are considered to be the most powerful pirates in the world, as well as having a powerful crew. Because of their power, they can declare chosen locations as their own; the mere declaration is often enough for others, both Marines and pirates alike, to acknowledge their authority. In fact, in the New World, they each have a territory that they govern. These territories benefit from the protection the emperors provide, keeping the borders safe from any faction that might want to invade them. It is only with the combined efforts of the Marines and the Shichibukai, as well as the distrust among them, that keeps their power in check. During the Battle of Marineford, the Marines and Shichibukai needed to fight together to engage just one of the Yonko and his crew.
The Yonko themselves are not allied together as a coalition compared to the Shichibukai and follow their own individual paths. The possibility of two or more of the Yonko forming an alliance is enough of a threat to cause the World Government to panic, as seen when the World Government attempted unsuccessfully to prevent a meeting between Shanks and Whitebeard at one point in the series. The World Government feared that the two Yonko may unite together and create a stronger threat. A war between two of the Yonko is considered an epic crisis, as Shanks' interception of Kaido's advancement on Whitebeard had taken the Marines by shock and awe, putting the World Government in a "cold sweat" as stated by one of the Marines.
In the decisive Battle of Marineford, Whitebeard, one of the Yonko, met his end towards the climax of the Whitebeard War. Blackbeard, his assassin, subsequently usurped his position. Shanks, another member of the Yonko, arbitrated a ceasefire to end the aforementioned war.
As an entity, the Yonko are one of the three great powers of the world, the others being the Shichibukai and Marines. Their strength and influence are such that they live quite literally as though they are emperors, doing mostly as they please. Individually, they are considered to be the most powerful pirates in the world, as well as having a powerful crew. Because of their power, they can declare chosen locations as their own; the mere declaration is often enough for others, both Marines and pirates alike, to acknowledge their authority. In fact, in the New World, they each have a territory that they govern. These territories benefit from the protection the emperors provide, keeping the borders safe from any faction that might want to invade them. It is only with the combined efforts of the Marines and the Shichibukai, as well as the distrust among them, that keeps their power in check. During the Battle of Marineford, the Marines and Shichibukai needed to fight together to engage just one of the Yonko and his crew.
The Yonko themselves are not allied together as a coalition compared to the Shichibukai and follow their own individual paths. The possibility of two or more of the Yonko forming an alliance is enough of a threat to cause the World Government to panic, as seen when the World Government attempted unsuccessfully to prevent a meeting between Shanks and Whitebeard at one point in the series. The World Government feared that the two Yonko may unite together and create a stronger threat. A war between two of the Yonko is considered an epic crisis, as Shanks' interception of Kaido's advancement on Whitebeard had taken the Marines by shock and awe, putting the World Government in a "cold sweat" as stated by one of the Marines.
They can motivate others to become pirates, such as Shanks inspiring Luffy. On top of this, the influence these pirates have over others is far greater than any other noted group. With one declaration, the slave trade and pirate attacks on Fishman Island stopped after the island was declared to be under Whitebeard's control.
After the timeskip Trafalgar Law cited that there are only two methods of surviving in the New World, and that is to be protected serving under the umbrella of a Yonko's dominion or to constantly oppose their authority. At least Teach and Kaido are both gaining influence and strength in the form of amassing Devil Fruit powers, both in their own unorthodox methods. Because of their immense power, it is necessary for factions aiming to oppose them to first strike an alliance with other factions in order to bring the Yonko down. The first of the Yonko to be introduced was Shanks who visited Luffy's hometown ten years before the story began. It is unknown if the Yonko existed at this point of time. The second was Whitebeard, one of the only two men to tie in a fight with Gol D. Roger, the Pirate King. Whitebeard was also later announced as the strongest man in the world upon Roger's death. Some of the Shichibukai fought the Yonko in the past; Shanks and Dracule Mihawk frequently dueled in their younger days, Gekko Moriah fought Kaido, and Crocodile fought Whitebeard.
All of the Yonko seem to have strong fleets, including huge ships and elite crewmen. All Yonko have traveled to the New World at some point in their past, where they are currently locked in stalemate, unable to progress any further into the Grand Line. This is a product of the combined efforts of both the Marines and Shichibukai, as well as the presence of the other Yonko in the Grand Line. Until recently, the World Government has been fine with the world powers remaining as they are. With the Yonko stuck in a deadlock situation, this allowed the world to remain stable. However, with the absence of Crocodile, defeated at the hands of the Straw Hat Pirates, the World Government was alarmed that two of the Yonko, Shanks and Whitebeard, arranged to meet each other. Later, with Enies Lobby in ruins, the Marines saw another defeat in the New World when a blockade failed to prevent the two from meeting.
Shanks vs. WhitebeardShanks and Whitebeard clash.
Fearing the two crews might form an alliance, the World Government anxiously waited to know the outcome of the meeting. After Shanks meets with Whitebeard, his presence upon boarding the ship causes a majority of the crew to collapse. He shares sake from his hometown in a token of friendship with Whitebeard as he brings him a grave warning. Shanks tells him that he believes the days of Whitebeard as the strongest pirate are coming to an end, warning him of the new era to come. With Marshall D. Teach making his advance to prominence and he will depose Newgate from his throne. Whitebeard stubbornly refuses Shanks' warning and the two clash. Upon the collision of their swords, the sky seemingly splits in half to the horror of both crews and their members. Afterwards the two depart and Whitebeard continues towards Marineford. In an attempt to rescue his 2nd Division Commander, Portgas D. Ace, Whitebeard attacked Marineford summoning all of his forces from the New World. Kaido attempted to attack Whitebeard; however, he was intercepted by Shanks. During this battle against the Marines, Whitebeard revealed how debilitated he had become over the last two decades, and that he continues to suffer more critical damage from his adversaries in his weakened state. During his battle he destroyed most of Marine Headquarters. He was successfully able to defeat two large Giants with ease and withstood the combined efforts of the three Admirals. He was able to help free Ace and defeat Admiral Akainu after he executed Ace.
Red-hair at marinefordShanks with his crew arrive and bring the war to a close
Remaining at Marineford alone to resolve the conflict with the Marines, Whitebeard was ambushed and ultimately perished at the hands of the Blackbeard Pirates, leaving only three Yonko. Shortly afterwards, Shanks arrived at Marineford with his crew. His presence rescued the remaining allies of Whitebeard and brought the war to an end. Shanks challenged Blackbeard, to which he turned down before escaping with his crew. According to Eustass Kid, due to Whitebeard's death, the Yonko have now been reduced to three, and the balance of the Three Great Powers has collapsed, which led to chaos around the world. Indeed, islands that were once under Whitebeard's protection, such as Fishman Island and Foodvalten, were under attack by pirates.
Some time after the war, X Drake arrived at an island belonging to Kaido, which is stated to be one of the Yonko's favorites. Upon asking "Iron Boy" Scotch, if attacking him would gain Kaido's attention, Scotch replied with the answer: "Yes". Drake changed into his dinosaur form and began attacking the cyborg. Also, the Gorosei hypothesized that Blackbeard was the pirate closest to obtaining the vacant position in the Yonko due to his possession of two Devil Fruit abilities and having complete knowledge about Newgate's sphere of influence. After the death of Whitebeard, Big Mom took over as protector of Fishman Island in exchange for Fishman Island paying a large amount of candy to the Yonko every month. When the candy factory was demolished during the uprising of the New Fishman Pirates, Fishman Island might provoke Big Mom's wrath since the island does not have enough candy for the tribute. Monkey D. Luffy has pledged that he will claim Fishman Island as his protectorate by defeating Big Mom. Teach has also usurped Whitebeard's position as the fourth Yonko, as the Gorosei predicted, having managed to conquer most of Whitebeard's former territory and becoming stronger by hunting down powerful Devil Fruit users and taking their abilities after killing them.
According to Caesar Clown, Kaido has assembled a battalion of Zoan Devil Fruit users using SMILEs provided by Donquixote Doflamingo. During the events of the Punk Hazard Arc, Trafalgar Law offered Monkey D. Luffy an alliance to depose Kaido, to which Luffy agreed, but also insinuated that he would overthrow all four. Eustass Kid, Basil Hawkins and Scratchmen Apoo also came to an agreement and formed an alliance. When Kid saw that Luffy and Law had formed their own alliance, Kid was sure that they were also targeting a Yonko and he wondered who they were targeting.
to be continued... :)