The Yonko, being four of the most formidable pirates in the One Piece world, possess incredibly powerful Devil Fruits and formidable Haki abilities. Their immense strength deters the World Government from meddling in their affairs.
A Yonko easily has the capability to conquer a country and establish it as their own territory. In some cases, weaker nations willingly align themselves with a Yonko to safeguard against potential threats. As a result, they come under the Yonko's control and become their operational base. Here is a list of the identified islands in One Piece that are under the protection of the Yonko.
6 Fish-Man Island
Fish-Man Island, located on the route to the New World, has gained the protection of several powerful Yonko. This has attracted numerous pirates who often make a pit stop on the island before continuing their journey. Unfortunately, these pirates, true to their nature, frequently show disregard for the island's inhabitants by initiating unnecessary attacks.
The islanders have long been plagued by these relentless pirate raids. At some point, Whitebeard took control of the territory, which acted as a deterrent to trouble-causing pirates due to his fearsome reputation. Following his demise, Big Mom struck a deal with Jimbei and assumed responsibility as the island's guardian. Finally, upon his arrival, Luffy declared Fish-Man Island as his own territory.
5 Totto Land
Totto Land, situated in the New World, consists of various islands and serves as the primary setting for the Whole Cake Island arc. Under the rule of Big Mom, this cluster of islands aimed to bring together all races and promote unity. Despite Big Mom's unpredictable temperament, Totto Land maintained a relatively peaceful atmosphere.
In order to maintain control and prevent any uprisings, Big Mom assigned her children as ministers for the smaller islands, ensuring loyalty and compliance. Following Big Mom's defeat, it is possible that responsibility for these duties was passed on to Charlotte Katakuri, the formidable Sweet Commander.
4 Wano
Wano holds a rich history, giving birth to the unbreakable Poneglyphs and housing skilled swordsmiths who crafted legendary blades like Ame no Habakiri, Enma, and Shusui. The nation's borders were sealed off from the world for unknown reasons in the past, until it fell under the oppressive rule of Kaido, transforming much of the land into a desolate wasteland. Oden, a brave warrior, attempted to reclaim his homeland but was tragically betrayed and killed. Now, 26 years later, the Straw Hats and their allies arrived in Wano, working together to free the country from its tyrannical grip. Presently, Kozuki Momonosuke leads Wano as its ruler, strengthened by an alliance with the Straw Hat Pirates.
3 Elbaf
Elbaf, the land of giants, is renowned as the most dominant nation due to its inhabitants' immense power. The giants of Elbaf possess astonishing strength, effortlessly defeating countless pirates. However, their invincibility is not absolute, as demonstrated by Linlin's destructive rampage, which she conducted single-handedly.
The Straw Hats have yet to set foot on Elbaf, resulting in limited information about the island. In the Egghead arc, it was unveiled that Shanks and his entire crew visited Elbaf, where they were warmly received and hailed as heroes. Soon after, Shanks bravely defended the nation from the Kid Pirates, strongly implying that Elbaf falls under his dominion. The reasons behind Shanks' interest in this country remain unknown, but they will be uncovered in the forthcoming story arcs.
2 Hachinosu
Hachinosu, also known as Fullalead, is under the dominion of Blackbeard, the territory's ruler. Previously, the island was under the control of Wang Zhi, a former member of the Rocks Pirates. Hachinosu holds significant importance for the Rocks Pirates, which explains Wang Zhi's desire to govern it.
Blackbeard managed to overthrow Wang Zhi and took control of the island, although he required assistance from Koby. This incident, known as the Rocky Port incident, led to Blackbeard being hailed as a "Hero." Blackbeard intends to transform Hachinosu into a nation aligned with the World Government. Given Blackbeard's crafty nature, it is reasonable to suspect that he has a hidden agenda.
1 Sphinx
Sphinx, the impoverished island where Edward Newgate hails from, was abandoned by the World Government due to its inability to meet the Heavenly Tribute. With time, lawlessness took hold, leading to infighting among the residents. To evade threats, the remaining inhabitants established a covert village.
Once Whitebeard rose to prominence as a notorious pirate, he consistently provided resources to the island's population. Although Sphinx was never officially under Whitebeard's control, it undoubtedly benefitted from the same privileges enjoyed by territories led by other Yonko. Following Whitebeard's demise, Marco shouldered the responsibility and became the protector of Sphinx, utilizing his Devil Fruit powers to heal the locals.