The Mantellian Separatist Movement was an organization formed on Ord Mantell during the Cold War in opposition to the Galactic Republic.
After the Treaty of Coruscant, many planets seceded from the Galactic Republic to join the Sith Empire or pursue independence. The corrupt planetary government of Ord Mantell

Ord Mantell Planet

opted to remain loyal to the Republic. However many on the planet desired the independence of their world. The resulting separatist movement sparked a civil war

Mantellian Separatist Crisis Event Cold War (3653BBY - 3642BBY)

on the planet, with the government receiving backing from both the Republic and elements of the criminal underworld.
The Ord Mantell separatists established a network of underground bases from which they launched guerrilla attacks on the Ord Mantell government and Republic targets. The attacks resulted in the destruction of the Ord Mantell landscape and the destabilization of the local governments. A primary base of the separatists was a large volcano. Located on the island of Avilatan, the heart of the volcano was a Separatist stronghold used to conduct meetings and organize separatist forces. Separatist leaders often met in the stronghold. Another major base was the island of Mannett Point. After invading the island, Separatist forces captured large amounts of Republic munitions, and used it against government and Republic forces. Such munitions captured included small arms and rocket launchers.
The Separatist movement held large portions of the island of Avilatan. Separatist forces fought for control of several villages on the island, including Drelliad and Talloran villages. In addition, the Avilatan Badlands were a hotly contested area. Separatist forces claimed much control of the Badlands, and led raids against Republic convoys.
While the Separatists were mostly a ragtag group, they had some degree of standardization among their weapons and equipment. They preferred various variants of yellow and red accented A16 military armor, while some wore various civilian clothes with a different pieces of various armor attached. Their preferred headgear was G3 military full helmet, which they frequently used to depict separatist warriors on the propaganda posters.

Armor

A18.MERC01 Mercenary Armor

A16.M04 Military Armor

A16.M06 Military Armor

A16.M07 Military Armor

A27.PLT01 Pilot uniform

A27.PLT02 Pilot uniform