The South Seas Alliance is a faction that emerged in the aftermath of the One Year War. The SSA took advantage of the post-war turmoil in a attempt to break away from the Earth Federation. The SSA was depicted in the Gundam Thunderbolt manga and its ONA adaptation.
The South Sea Alliance is a collection of former nations in South Asia that are part of the Earth Federation. Its system of government or general political outlook is unknown currently in the series, but it is known that the country suffered massive devastation from the Colony Drop of the One Year War which saw tsunamis smash coastal areas. Despite being part of the Federation, their mobile suit forces are largely comprised of salvaged Zeon mobile suits and technology.
After the devastation and losses suffered during the One Year War the emotional trauma left on society was great. Capitalizing on people's desire for guidance and need for something to have faith in, a religious ideology emerged in this post-war environment called The Order, led by Sojo Levan Fu. Levan Fu was a child test subject for experiments regarding Newtype abilities, however the process of these tests severely damaged his brain, leading to a diagnosis of a year to live. Instead of accepting terminal care, Levan Fu became a Federation officer in charge of a mine sweeping and causality collection vessel during the war. The effects of his role during the war was that Fu was able to collect and "save" deceased individuals who would have otherwise been lost in space. This contact allowed him to use a combination of his new religious ideology and a manifested Newtype ability of charisma and emotional zealotry to grow a large amount of followers.
In turn these followers join in Sojo Levan Fu's endeavors to save and salvage people and machines from the war, which they then would try and convert or repair them for their own purposes. Two people saved during this time by these salvage and rescue ships later played an important role furthering the Order's growing power, J.J. Sexton; who would bring his knowledge of the Reuse "P" System and Claudia Peer; who would bring her military knowledge and leadership. At some point this religious following grew so big it dominated the South Seas Alliance to where now the country is a virtual theocratic society ruled by the orders' religious and military hierarchy.
Six months following the end of One Year War, the South Seas Alliance plotted to declare independence. Both the Earth Federation and Zeon Remnants received intelligence that the South Seas Alliance were building a Psycho Zaku and launched incursions into their territory. A Zeon squad of Acguys managed to infiltrate SSA territory via underwater to recover a spy who had spotted J.J. Sexton while the Federation ship, Spartan, engaged in an aerial battle with an SSA border patrol led by Claudia Peer. The SSA took heavy losses in mobile suits and Dodais in their attempts to repel the invaders.