G-5, also known as the Marine "Grand Line" Fifth Branch,, belongs to the more major Marine Bases in the One Piece world. It is located in the New World, not far from the Red Line, thus positioning it as a key vanguard of the naval forces of the World Government. Given that it is located in the New World—a place characterized by its rough and unpredictable conditions—distinguishes the base itself and touches on its character and the people inside it.
The existence of G-5 was brought to the forefront by Marine Admiral Aokiji right after the Summit War of Marineford, a climactic event in the One Piece storyline. Mentioning G-5, Aokiji referred to it as a base "full of problems," thus indicating its not-so-good reputation inside the Marine organization.
One of the notable parts of G-5 would have to be its leadership. Vice-Admiral Smoker, known as "The White Hunter," is the Commander of the G-5 Marine base. He got appointed to this position after the betrayal and subsequent exposure of his former superior, Vergo, which created something of a mystique regarding the recent history of the base. In concert with him, Captain Tashigi assumes a great role in G-5's operations.
The rank and file Marines stationed at G-5 are a peculiar lot with a reputation for being the wildest. They rank first in the most undisciplined of all Marine units. This disposition can be explained by their origin and placing in the New World, which is reputed to be the cruelest and wildest sea in the One Piece World. It is as if the harsh environment of the New World has made its way deep into the temperament of those Marines, making them like the local people in being stern of will and able to withstand the challenges of the treacherous region.
G-5's strategic importance is reflected in its activities. For instance, Vice-Admiral Smoker and Captain Tashigi, with their G-5 underlings, have been seen to intercept the fleeing Fishmen pirates who just escaped from Fishman Island into the New World. This blockage makes G-5 a powerful block against advancing pirates into the furthermost dangerous territories of the Grand Line.
Another of the more interesting facts with G-5 is that his birthday corresponds with the protagonist of the series, Monkey D. Luffy. Both Luffy and G-5 have the same birthday, May 5th, more commonly known as Cinco de Mayo. The day was highly historic for the Mexican army since they defeated the reigning Napoleon III in the Battle of Puebla. Though simple enough in its connection, such a detail—within the highly-woven narrative of One Piece—may often be found to hold added meanings or serve as foreshadowing for following events.
The Marines of G-5 have been part of some of the major events that have taken place in the One Piece storyline. In this process, their involvement with the Straw Hat Pirates and particularly Luffy is interesting and is something gaining many fans follow up to since Smoker was still a captain in Loguetown. Now it is speculated if Smoker is still going to keep on remaining a rival to Luffy, as the power gap has continued to be too wide.
Though the G-5 Marines are naturally unruly and are found to be quite good fighters, their very existence in the New World does give off the message that they are amongst some of the skillful and tough members of the Marine forces, which do happen to be so because of the calibers of pirates and other threats met within this part of the Grand Line.