G-5, officially Marine Grand Line 5th Branch, is a Marine Base located in the New World, near the Red Line. It was first mentioned by Aokiji after the Battle of Marineford and according to him, it is full of problems. Smoker requested a transfer to this branch in order to "keep his targets close".
The headquarters of the G-5 location has several buildings left tattered or broken and slightly fixed from damages and appears to be left in ruins.
It is said that the Marines of this branch are insane, cruel, and merciless people who stick needles into pirates, feed them to sharks, or use them for campfire kindling. Although these actions are considered just rumors by some pirates, some were proven true when some of the Marines lit a captured pirate on fire and repeatedly stabbed another pirate while hanging him. They are known for not following the orders of their superiors, however, they seem to obey Smoker mostly by merit of intimidation and a mild respect for his great strength. Some members do not wear the full formal Marine uniform (if anything, they are overly-casual to the point of wearing slacks and a bucket for a hat) and act flirtatious toward their female superior, Captain Tashigi, although they do respect her as they tried to protect her from Law and took her with them to escape from Law's sphere and reassemble her body. They do appear to not be entirely fearless, as they were hesitant to follow the Straw Hat Pirates to Punk Hazard, which the Marines had declared that no one, pirates and Marines alike, should set foot on, for remnants of poisonous gas supposedly wreathed the island.
Regardless of their ruthless reputation, they seem to be easily frightened when they meet highly infamous people such as the Seven Warlords of the Sea Trafalgar Law and his pet dog Jupiter. They too were helpless against the dangers of nature as seen when they panicked when a large piece of ice floated toward their ship. While initially hostile towards the Straw Hats, the members of Unit 01 willingly cooperated with them in order to defeat Caesar Clown and rescue the kidnapped children. During the ordeal in Caesar's facility, they even come to respect the Straw Hat crew. Even before the events on Punk Hazard, they appeared to have a great sense of comradeship, as they always tried to save their injured teammates during emergencies and even returned to the battle between Law and Smoker to save Tashigi. Despite these failures it can be said that they are quite strong as they are able to survive and operate in the merciless New world where most men are crushed by the climate and numerous pirates.
The G-5 is split into at least six divisions, with Smoker in command of Unit 01, and Yarisugi of Unit 06. The overall leader of the entire G-5 unit was Vergo, who acted in amiability in contrast to the majority of his subordinates, but is in truth a deep cover agent planted in the Marines by "Joker". His duplicity was discovered by Smoker and his second-in-command Tashigi, but they decided to keep it a secret for the sake of their subordinates, who admire him. He was defeated by Trafalgar Law and Smoker and left behind to die in the collapsing SAD production room.