The Osarian-Rhommamool conflict represents a drawn-out period of intense strife between the twin planets of Osarian and Rhommamool. This occurred around 25 ABY, marking the beginning of the Yuuzhan Vong War.
The fundamental cause of this conflict stemmed from the stark contrast between Osarian, a planet of opulence and affluence, and Rhommamool, a barren and scarcely habitable world. Over time, Osarian populated Rhommamool with criminals who were effectively used as slave labor in the planet's mines. The profits generated from this labor were largely used to sustain the extravagant lifestyle of Osarians. Despite sharing a unified government, it was centered on Osarian and predominantly controlled by Osarians.
The situation remained relatively stable because neither planet possessed significant spacefaring military forces. However, every decade, their orbits would bring them within a million kilometers of each other, a distance close enough for ground-based nuclear missiles to reach their targets. During these periods of close proximity, tensions would escalate. Prior to the close encounter in 25 ABY, both worlds managed to refrain from launching attacks against each other.
Leading up to 25 ABY, a charismatic and radical figure named Nom Anor gained prominence on Rhommamool. He combined his animosity towards the Osarians with a broader condemnation of technology, the New Republic, and the Jedi Knights. He established an independent senate and a group of fanatical religious followers known as the Red Knights of Life to advance his agenda.
Anor's calls for action against Osarian prompted the New Republic to deploy a Mon Calamari Star Cruiser, named the Mediator, to maintain order. Simultaneously, Jedi Knight Wurth Skidder arrived to take independent action against whichever side initiated aggression. The Osarian leader, Shunta Osarian Dharrg, employed Captain Grappa and his Osarian First-Force to aid in the defense of their world. Despite the arrival of Leia Organa Solo to mediate negotiations, a resolution proved unattainable. This was because Anor was fully committed to exploiting the situation to create maximum destruction and chaos. Following her departure, Anor incited his followers into a state of religious fervor and initiated a nuclear strike against the Osarian capital, Osa-Prime, thus igniting a full-blown war between the two planets. Rhommamool launched additional missiles, resulting in the destruction of more Osarian cities. Enormous red thermonuclear blast clouds were observed over the planet, presumably causing devastation to millions of Osarians.
Anor, employing a nuclear-armed shuttle to both simulate his own demise and disable the Mediator, secretly departed Rhommamool in a concealed A-wing with his assistant Shok Tinoktin as the nuclear bombardment continued. As the conflict intensified, the Red Knights of Life attempted to assist the Yuuzhan Vong in their conquest of the galaxy by attacking planets with advanced technology and droids, including Osarian and Uffel. However, they were successfully repelled by the Iron Knights.