Originally, there was an Ancient Kingdom with advanced civilization and technology. At this time, the Red Line and Grand Line has already existed, they divided the world into 4 seas just like in current days. Ancient Kingdom saw Red Line and Grand Line as a huge problem in connecting the world and therefore, they devised a plan of destroying the Red Line. And so, the ancient weapons were created for this plan – the One Piece plan.
If we check out the map of One Piece, there is a spot called Reverse Mountain where Red Line and Grand Line meet. According to the Ancient Kingdom’s plan, if this area was destroyed, the Grand Line and Calm Belts would also disappear, resulting in the connection between the four seas. Of course, this would make the world become whole and that’s why the plan called “One Piece”. Next, after Reverse Mountain’s destruction, this area would connect all the four sea and created the legendary sea – All Blue.
Unfortunately, the Ancient Kingdom was defeated by certain forces, and their history was deleted from the annex of time. Then, these forces formed World Government as we see today. After hundreds of years, Gol D. Roger found the true history and the origin of the World Government. He wanted to reveal the truth and took down this government.
However, Roger believed his pirates alone wouldn’t be able to accomplish this. Therefore, he came up with a plan of intentionally letting himself publicly executed, and before the execution, he announced the mysterious treasure One Piece. This totally hyped up the “pirate trend” and ushered the Golden Age of Pirates. This Golden Age will mark the revolution and one person will inherit Roger’s will.
We believe that Luffy and his friends will successfully travel to Raftel and discover the true history like Roger did. Soon, Luffy with a pirate alliance will bring war to the World Government and the pirate alliance will emerge victorious. Then they use the ancient weapons of the lost kingdom to destroy the Red Line, uniting all the four seas, thus forming the fabled All Blue. Finally, Luffy will become the Pirate King as the one who united the world.