The South Seas Alliance (南洋同盟 Nan'yō Dōmei?), known as the Nanyang Alliance in the Viz Media translation, was a faction that emerged in the aftermath of the One Year War. The SSA took advantage of the post-war turmoil in an 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 was an autonomous region within the Earth Federation that held de facto control over the Far East, South East Asia, and Central Asia following the One Year War. Its territory suffered massive devastation from Operation British, causing severe flooding in certain areas.
90% of its citizens were believers of Nanyang Buddhism, a school of Buddhism that predates the Universal Century. Its military forces consisted of poorly trained but fanatically loyal monk soldiers. Most of its weapon were salvaged during the One Year War, such as the MS-07B Gouf (Thunderbolt Ver.). In the manga, it also made use of salvaged Type 61 Tank and Dabude-class land battleships.
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 school of Buddhism called Nanyang School rose to prominence, 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 assisted the Federation by leading a minesweeping and casualty 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 number 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 rebuilding the 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.
Eventually, the SSA's reason for constructing the Psycho Zakus was revealed: using 32 Psycho Zakus, Levan Fuu intended to suppress the 32 colonies of Side 3, take over the Solar Ray, and use it to destroy the Anaheim Electronics facility on the moon, which Fuu saw as the true instigator of the war.