From many seemingly empty lines in the story of One Piece one is a clue to understanding a truth.
The phrase of Dracule Mihawk “One by one, he turns the people around him into his allies. More than anyone else sailing the seas… That man possesses the most terrifying power” that describes Luffy who not only had a small army following him but other people joining to help him during the Paramount War.
What is this “Power”? I would say it’s Haki, Luffy’s own will(power). To be specific his Conqueror’s Will.
As Rayleigh explained on Rusukaina you can’t train your Conqueror’s Will like other types of Haki, you can only learn to control it.
- You have to improve your character to strengthened it. So someone’s charisma and personality determine the strength of his Conqueror’s Will. By being mentally stronger man you will be a stronger “manipulator”.
- Conqueror’s Will overpower the will of you’re opponent. This could be seen as knocking them out as is always is, but what about the subconscious? I think that a strong user of Conquer’s Will is able to change the way people feel and think about something, influence there decisions.
A strong user of Conquer’s Will can manifest his spirit in such a way to make people feel, think or act as he desires. This could be only partly effective on more individualistic and strong person and is not out right mind control.
This would explain why Zoro first turned down the invitation to join, why both Nami and Robin couldn’t leave the crew, why people close to Luffy proclaim that he will be the Pirate King and cities of people try to protect him.
But not only Luffy can do this. Blackbeard too made instant allies out of Impel Down prisoners. Whitebeard had all the surrounding people acknowledge him as their father. Doflamingo became the boss of his former bosses, who now think of him as a king above all.
And Roger himself by just telling about a live of adventure to a lazy stranger convince him to journey the world round and be free as can be, even though Rayleigh first laughed at him as a fool.
A true King shapes the minds of the ones following him.
*Theory by Kizoku. LyLord