The world of One Piece is a strange one, from a political perspective. There are three factions I want to take a closer look at, in hope of understanding their relation: The World Government, the Shichibukai and the Yonkou. I'm pretty much going to ignore the Marines in this, as they are fairly irrelevant for this, as they are but a tool for the World Government. This is not gonna be my best ever post, but what ya gonna do?
The World Government
Let’s start off with probably the most complex of the three, the often hated, “all powerful” World Government. I’m going to start with a brief summary of the history and workings of the WG as well as a perhaps controversial real world comparison, before delving a bit deeper on their organization. When you look at the World Government, immediate comparisons can be drawn to the United Nations. They are both made up by the majority of nations in the world, they were both started after what we can assume was a massive war, they both have an army to one degree or the other and both have the upholding of peace, of law and order as their prime objective. According to Spandam the World Government is made up out of over 170 countries, the UN has about 20 more. The World Government was started by the “Twenty Kings”, the ancestors of the World Nobles, after the war against the Ancient Kingdom. The United Nations were formed after World War 2, after the League of Nations, failed in their efforts to prevent it. Both the WG and the UN, hold an army of sorts, with the main difference being that the Peacekeepers are neither a standing army, nor an army to be offensively used. Their prime objective, keeping the peace, remains the same however.
Now I’ll try to get a glimpse of how the world government functions on an organizational level. The two most telling aspects of that are the Gorosei and Reverie. Reverie is held once every four years. That tells us that it essentially has no power over day to day, and probably not a whole lot over long term matters either. No council that only meets so rarely can be anything more than a prestige façade, albeit a one with certain uses, as being invited into Reverie offers privileges. With Reverie essentially powerless though, that leaves a power vacuum inside the World Government, a power vacuum that is filled by the Gorosei. They handle the day to day runnings of the World Government, that includes giving the order to execute ace, studies on how to to turn humans into giants and covering up embarrassing defeats, for their vassals, such as Crocodile or Moriah. Some of the things they do, such as genetic experiments, also leads me to the conclusion that Reverie is essentially powerless and that the Kings and rulers in it, barely control their own lands. Rulers such as Iceburg or Cobra would never have stood for genetic research on children, I doubt they even know. The World Government, or rather the Gorosei, decided to cover up the fact that Crocodile was the leader of Baroque Works, something that, as far as we know, isn’t even widely spread knowledge in Alabasta, where Cobra would have plenty of reasons to make it known. The only thing we do not know about the Gorosei, which would have been helpful in ANALysing them would be the answer to the simple question: How does one become a Gorosei? That would really tell us a lot about the workings of the WG, whether it's a dictatorship, ruling over the world by an iron fist, or whether they are but a proxy to the individual nations, although I doubt it. In short, the nations itself are almost meaningless, having to subject to the World Government and having no authority outside of their little islands.
The World Nobles, in my opinion, are irrelevant remnants of the civil war, clueless inbreds, who are obeyed because it is custom to do so, not because they serve any role in the governmental structure of One Piece.
The WG control two of the most important military powers in the world of One Piece. The Marines, who are under direct control, usually obey their orders to the letter, whereas the Shichibukai function more like mercenaries. The WG offers them immunity, they offer them support. I almost loathe to rank the Shichibukai as an important military power, because quite frankly they aren’t. Due to lack of strength on some, due to lack of allegiance on others and most importantly, due to the divisiveness amongst themselves. If they worked together they’d certainly warrant that title, but everytime we see more than one Shichibukai on screen, they come close to infighting amongst themselves. Another problem is that at their heart, the Shichi are pirates, pirates who have different objectives and allegiances than the WG they allegedly serve. Mihawk refusing to aid the WG at Marineford as soon as Shanks arrived is a good example, in fact the whole Marineford Arc somewhat lessened the importance of the Shichibukai for me. They are allegedly one of the three great powers, yet they barely played any part in the proceedings there. A battle that should have been a decisive victory for the WG, as 2 of the 3 great powers stood “united” against a single of the Yonkou, almost turned out to be a horrendous loss. The act of becoming a Shichibukai already marks them as dependent. It is not a title won by power, or by cunning, it is a given title, meaningless really and revocable at any time. Whether they themselves believe it, they are government dogs, and like even the most faithful dog, can and must be put down once they start randomly biting people.
Speaking of the Yonkou, they serve an interesting role as well. Four unallied parties, that divide the New World amongst themselves to some degree or another. I believe that united they’d be the strongest of the three powers, but due to their nature such an alliance is nigh impossible. The only ones that might have been considered allies were Whitebeard and Shanks, it is already known that Kaidou wanted to stop Shanks intervening at Marineford, a big Mom and Kaidou alliance is possible but I doubt it. And Blackbeard simply isn’t the type of guy to make real alliances, now that he has what he needs. Unless he sees a significant advantage to a temporary alliance, he would not enter one. A real world comparison one might make is to the Warlords that ruled large parts of China after 1916. Together they’d have been able to threaten anybody, but divided as they were, they were able to be picked off one by one.
Sry for the long and probably shitty post. Here's a dancing panda to make up for it.