Marineford

Marineford (マリンフォード Marinfōdo) is the main headquarters of the Marines (海軍本部 Kaigun Honbu, Marine Headquarters, Navy Headquarters in FUNimation subs). It is where Fleet Admiral Sengoku and the three Admirals reside, along with many Vice Admirals and lower officers when they aren't assigned to another base. The city surrounding marine HQ is inhabited by the families of marine soldiers. The Marine HQ is one of the three great powers, alongside the Shichibukai and the Yonkou.

It is situated near the Sabaody Archipelago, and lies directly next to Mariejois on the Red Line. The only safe way to reach here is through the Gates of Justice.

Shiki's Assault
Twenty-two years ago, after hearing that the Pirate King Gol D. Roger had been captured by the Marines and will face execution in Loguetown, the Gold Lion Shiki came to Marineford alone, in his angry refusal to believe the Marines would be able to capture Roger, and killed many soldiers in the process. Vice Admiral Monkey D. Garp and Admiral Sengoku then fought against Shiki together. After a fierce battle between these three men, half of Marineford was reduced to rubble, many were injured or killed, Shiki was defeated, captured, and incarcerated in Impel Down.

East Blue's Newest Pirate
Shortly after the defeat of East Blue's most powerful pirates in the hands of Monkey D. Luffy, the higher officers here granted him his first bounty of 30,000,000.

Vice Admiral John Giant then announced to every high-ranking officers that the Marines there must be prepared to serve justice with all their might, and that there is no room for cowardice or moral justice.

Overtime, Fleet Admiral Sengoku spent his time residing here, giving orders to lower ranking subordinates, and taking out his fury over Monkey D. Luffy's repeated actions on his grandfather, Vice Admiral Monkey D. Garp.

Marineford is the site of the Whitebeard War, this event is known as the Battle of Marineford which result the destruction of HQ.