source: Wikipedia

Monkey D. Dragon is the father of Monkey D. Luffy and the son of Vice-Admiral Monkey D. Garp. Known as the Revolutionary Dragon, he is the world's most wanted criminal, and another one of the several characters given the middle initial "D". He has had his revolutionary ideas spread throughout the world and has taken several nations. He is also the only member of the D. family to look serious, partly due to his strange facial mark. Despite being an enemy to the World Government, he still keeps contact with his father.

Before the start of the series, Dragon left Luffy in Garp's care. Dragon first appears after a lightning bolt suddenly destroys the gallows where Luffy was to be executed by Buggy the Clown and then saves Luffy from being captured by Captain Smoker. When he saved Luffy from Smoker, a mighty gust of eerie wind swept through Loguetown. It is undetermined whether or not he was the cause behind the gust of wind or the lightning; however, the story leads to believe there is more to him than it seems. Recently, he has taken over an island in the South Blue and is about to head to the North Blue when he commented, after noticing Luffy's newest bounty, given to him after invading Enies Lobby, that father and son will meet sometime soon.

Vice Admiral Garp (Marine)
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        | father of
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        V
Monkey D Dragon (Revolutionary/ Rebel)
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        | father of
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        V
Monkey D Luffy (300M Beri Pirate)

At first glance, the World Government seems to maintain a worldly order that benefits all, making the world safe for the sake of everyone. Using the Navy, they pursue criminals endangering the lives of those who are innocent, protecting the people of each country in the world. The World Government is the largest World Power maintaining full rights to halt or encourage any political action without question or opposition from any side.

The reality though is that, unknown to most citizens (and many world leaders), the World Government's actions are secretly and often based on corruption or questionable motives. Often when the storyline involves them, it shows them hiding the truth or ignoring the rights of the people. Individuals who become the enemies of the World Government are ruthlessly hunted down and dealt with and all those who walk along the same path as them are doomed to share the World Government's fury.

The World Government's power to release any information on anyone or anything they choose often cause the truth being hidden, altered or ignored all together. Any countries attempting to protect or harbour criminals are at risk from the World Government, although what would happen exactly has not been addressed yet. For the most part, the important role in maintaining world stability on a political ground far outweighs the corruption they often display.

Often there is a 'holy' or 'just' theme to the naming of things related to the World Government, like 'the Just Eleven Jurymen'.