The army of Pacifistas in One Piece could be the strongest army of soldiers in the series that is under the World Government. Introduced during the early episodes of the series, this army got stronger with time due to some modifications.
These Pacifistas do not attack higher authority officials since they are soldiers of the World Government. These higher authority officials include the seven warlords of the sea, the Five Elders, and the ruler of the World Government, Imu. But there could be some modifications done to them by their creator, which were creating problems for the World Government during the Egghead arc.
The creator of these soldiers is Vegapunk, the genius scientist who used the body of Kuma as a base to mass-manufacture these killing machines. Currently, Bonney, the daughter of Kuma, holds the authority to command these machines, and not even the Five Elders can grab the authority to control them, even though they have the highest authority on Egghead Island.
Disclaimer: This article contains potential spoilers from the One Piece manga series and has the author's opinion
One Piece: Why the Gorosei cannot control any Pacifistas on Egghead Island
The Five Elders cannot do so because Bonney has the highest authority over the Pacifistas, as granted by the creator of these robots, Vegapunk. He did so to avoid the scenario of Bonney getting killed by these robots, who share the same face as her father, Bartholomew Kuma.
After Saturn couldn't get a hold of Pacifistas and Vegapunk started to stream his message to the world, the former decided to summon all Five Elders and they started to destroy all the Pacifistas because they no longer held any authority over them.
Pacifista are World Government robots that were introduced in episode 399. These robots are replicas of the former warlord, Bartholomew Kuma, but do not share his devil fruit abilities, which come from Paw-Paw devil fruit.
These robots have strong lasers installed inside them, which they use against rebels, or, in other words, pirates. These robots hardly ever speak, but they utter the names of pirates after identifying them.
During the Egghead arc, the old Pacifista models were discarded, and new advanced models emerged known as Mark III Pacifistas. Moreover, a group of elite Pacifistas were also manufactured from the lineage factor of the warlords, known as Seraphim models. However, their control management remained the same as they were managed through the authority chip.
The authority chip is a computerized one that an authority person should have with them if they want to control these robots. The natural control hierarchy of these robots starts with the Five Elders holding the highest authority, followed by their creator (Vegapunk) and his satellites, then Vegapunk's bodyguard Sentomaru, and lastly some other holders like Lucci, Kizaru, and some others.
However, the creator of these robots decided to modify their systems in such a way that Jewelry Bonney, the daughter of Kuma, would have the highest authority over these robots.
Vegapunk did this, thinking it would be pretty inhuman of him to let Bonney die at the hands of robots who have the same face as her father. So, Bonney holds the highest authority in controlling these robots.
Due to this, Saint Saturn lost control over these robots and tried to kill Vegapunk. Although Vegapunk's life status remains a mystery, he started to stream the 'truth of the world' to the Grand Line, which forced Saturn to summon all the Gorosei to Egghead.
As soon as they arrived, Saint Nusjuro dashed forward in his devil form and started slashing any Pacifista that came into sight because these robots were no longer in control of them, and getting rid of them could have been the only choice.
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