Before i share this theory please remember this isnt spoiler it does has some recent episode content a bit , but its just a theory. Also for all the One Piece fans please take a deep breathe and a glass of water for this as u may FREAK...
Roger’s will that Whitebeard was talking about, it actually wasn’t his original will. Roger inherited it as well from waaay back then, from 800 years ago to be precised. Yes, it was originally the will of The Ancient Kingdom (let’s call it AK from now on). The AK was a big kingdom, it ruled over almost the whole world (just like WG does now). They apparently also had a pretty-advanced civilization. One could say that there’s almost nothing they couldn’t achieve with everthing they got at the time.However they had an issue. As we know, the planet of OP contains of big four seas, east, west, north, and south, each were separated by the Red Line and the Grand Line. The AK saw Red Line and Grand Line as a big obstacle because they have been been preventing people from traveling from one sea to another, thus preventing the AK from reaching its full prosperity as well.And So they made this project, an insane one, but has to be done. The project was about eliminating the Red Line and Grand Line to fuse the 4 seas into one big ocean, the united ocean. The called it the project of “One Piece”. In order to do so, they started to build some weapons which will be strong enough to destroy the red line (later called Ancient Weapons)It turned out that not everybody was pleased by this project.. you know, politics. Some other kingdoms were totally against it, they smell a conspiracy was playing behind it. But the AK stood their ground no matter what. Guess what happened next? a huge war broke out. It’s the AK vs 20 kingdoms who were against the project of "One Piece”.
The 20 kingdoms came out as the victor and they declared themselves as The World Government. Meanwhile the AK was reduced to shred, along with all their historiy, and the “One Piece” project was never heard again since then...
Unexpectedly, The AK has anticipated their downfall. Before the war begun they had carved historical notes on these certain metals which as hard as diamond(later called the poneglyphs) and hid them throughout the world, along with the weapons they’ve built. The AK really wanted to make sure that their desire wouldn’t die in case of anything bad happened to them.
the WG was mad with this fact and completetely prohibit any form of poneglyph dechipering.
but it's too late, the will has been passing through ages since then… silently waiting for someone to recieve the massage.800 years has passed.BUT THEN a pirate named Roger sucessfully reach Raftel and discovered the true history. He knows exactly what to do, but unfortunately his body didn’t allow him to… he had this incurable disease, remember? whereas the project needs a lot of power and time to complete, 2 things that Roger didn’t have that time.
Therefore, he decided to create The Golden Age of Piracy instead, hoping that there will appear someone who is strong and righteous enough to complete the massage in his place.
Who will be that ‘someone’? I think we all know the answer. :D
The idea of “One Piece” is to create a united ocean, a perfect ocean to sail. Therefore we have two jobs : fusing all the seas into one and eliminating Grand Line abnormality. GL’s abnormality? Is that even possible?
Apparently it is possible for the AK scientists. The trick is destroy a spot where every sea on the planet (north, west, east, south, grand line, new world, and calm belt) meet in one place. There is a spot like that? Actually, there are two, and both need to be destroyed. The two spots are reverse mountain and mariejoa/fishman island. ( I talked about this is my last theory please check if curious about it more.) Losing a huge mass of land, The sea became even more unstable than before, a big whirlpool will appeared on the center of destruction spot, storms and tidal wave occuring everywhere. However they’re only temporary, after a couple days the raging storm shall be subsided.
And then, the magic began…
disastrous random-weather on grand line and NW suddenly doesn’t occur anymore
the magnetic field which make a normal compass useless are completely gone
Even the wind starting to blow on Calm Belt
How about sea monsters? Well, this is the time where Poseidon come to play. The Poseidon has fully taken control of the sea king and make them some kind of ‘police’ of the ocean to prevent other sea monsters from going wild. (yes I do think this is very possible). If u dont know Poseidon was the former princess who controlled sea kings (shirahoshi)
The ideal united ocean is finally created . The project of One Piece officialy succeeded!!
But is that it???
It’s not. There’s actually one more after-effect, and it’s the most important one.
The big whirlpool that appeared after the destruction of reverse mountain, It happened because the water mass of the four seas simultaneously flowed into the center of destruction -- the place where reverse mountain was stood once. Logically, that means every kind of living things which originally lives in four seas were brought there as well. You literally could find every fish species from all over the world here.
Wait, was that sounds familiar? Exactly, the destruction spot has became that legendary mythical sea…
Joy Boy is the AK King. And so for his people he created the Noah(giant ship) for his people knowing that this day will come....my last theory covers the noah part more but u get the main idea lol..
so pretty much one piece doesnt just happen...U MAKE ONE PIECE..