Void Century

Also referred to as the Blank Century, this is the period 800 years ago when a great civilization dominated the world and then at the end of the century they disappeared. At the end of the century the World Government came to power and censored everything that happened in the previous 100 years.

This period became known as the blank century because there is nothing left to acknowledge anything that happened, aside from the Poneglyphs which are written in a language that few know how to read. However, it causes a problem with the known histories of the world as nothing ties up because of that missing period, although most people do not seem to know about this information. For example, Nefertari Cobra after being told by Nico Robin about this missing period was completely shocked by its existence and didn't know there were parts of the world history that didn't tie in. Due to several pieces of evidience that appear in the storyline, many fans have come to believe that people with the initial "D" may be descendants of the race of the Void Century.

For the World Government, the events of this period are better left unknown as information linked to it is considered far too dangerous.

The years of this void century rages from 700-800 in the Age of the Sea

The void century was hinted during the Skypiea Arc, the numbers of date was found in Robin's flashback

The Great War
According to the Shandian chief in Skypiea, their ancestors known as the Shandorians fought with enemies who were out to obtain or destroy the stone(the Poneglyph) which was set during the Void Century.

In the age of the sea, 402; the city of gold Shandora propered.

Ancient Weapons
The world government lied to the public, saying that the reason to forbid the study of the poneglyphs was for fear of revival of the Ancient Weapons. The ancient weapons are the superweapons that may have been used for the war during the Void Century but as of now are not yet confirmed. Olny 2 weapons are metioned but were never shown. The Ancient Weapons known in the story so far are Pluton and Posidon

Ancient Kingdom
The real reason why the World Government banned Ponegyph research is that the World Govenment is afraid of the Ancient Kingdom's ideals. It held great power until the Alliances, which soon became the World Government, fought against the kingdom. Knowing that they will be defeated, the kingdom carved the Ancient Langauge onto the stones. All records of the kingdom were destroyed, yet somehow the name of the kingdom was learned by the Ohara research team and was almost revealed by Professor Clover.

Poneglyph
For the main article, see Poneglyph

The people of the Ancient Kingdom carved the ancient language onto the stone to tell the history of the kingdom.

Birth of the World Goverment
In 800, at the end of the Void Century, the World Government was born, they took political control of the world.