Before the Mandalorians launched their invasion of the Galactic Republic, the second major conflict of the Mandalorian Wars was the Battle of Cathar. During this battle, the Mandalorian Neo-Crusaders, under the command of Mandalore the Ultimate, seized control of planets bordering Republic territory. This battle led to the near total extinction of the Cathar species and later served as the pivotal event that drove Revan's Jedi faction to join the war effort.
During the time of the Great Sith War, the Mandalorians, then under the leadership of Mandalore the Indomitable, allied themselves with the Sith, who were led by Exar Kun and Ulic Qel-Droma. The Mandalorian Crusaders inflicted heavy damage on Foerost, Coruscant, Iridonia, the Abron system, the Thisspias system, and the Contruum system while under the command of Qel-Droma. The Cathar engaged the Mandalorians in combat, resulting in the defeat of the Mandalorians on Onderon. Mandalore the Indomitable met his end on Dxun.
Following Mandalore the Indomitable's demise, Mandalore the Ultimate took over and revitalized the Mandalorian forces by welcoming members from various species, transforming them into the Mandalorian Neo-Crusaders. Encouraged by the Sith with promises of a legendary battle, the Mandalorians enthusiastically agreed to invade the Republic.
As a preliminary step to invading the Republic, the Mandalorians initiated a campaign to conquer planets located outside of Republic territory. Remembering the humiliation they had suffered at the hands of the Cathar, the Mandalorians prioritized Cathar as one of their initial targets. Cassus Fett, Mandalore's chief strategist, was tasked with leading the assault.
The Cathar people were completely unprepared for the Mandalorian onslaught. Mandalorian military forces launched a coordinated attack from space, beginning with a surface bombardment that destroyed all interstellar communication relays and orbital spacedock facilities. Following this, they descended to the planet's surface, massacring the majority of the population in their sleep or as they attempted to flee. Cassus Fett's Basilisk war-mounts were instrumental in the destruction of the more primitive Cathar settlements.
Having previously fought against the Mandalorians during the Great Sith War, the Cathar understood the reason for their targeting and knew that no mercy would be shown to their species or their world. Because Cathar wasn't a member of the Galactic Republic, the Cathar were left to defend themselves. As the battle neared its end, Cassus gathered the remaining Cathar survivors near the ocean and gave the order for their execution. One Mandalorian voiced their objection, arguing that the Cathar were already defeated. However, Cassus declared that the battle was about exacting revenge and that he intended to eliminate all Cathar on the planet. He then commanded the execution of the remaining Cathar, resulting in the death of the objecting Mandalorian alongside them.
In a final act of desperation, the Cathar race gathered the last survivors capable of spaceflight and sent them off into the void aboard the few remaining ships. Juhani's family was among those who escaped on one of these refugee flights, eventually landing on Taris. However, the Cathar species as a whole was pushed to the brink of extinction due to the genocide on Cathar.
The Mandalorians did not halt their conquests after Cathar. They proceeded to conquer additional systems beyond Republic borders and ultimately launched an invasion of the Republic itself. In numerous engagements, the Mandalorians overwhelmed the Republic military, coming close to achieving complete domination of the Republic. However, the Jedi Order chose not to intervene in the war, as the Jedi Council believed that a more significant, unseen threat existed.
This stance shifted in 3963 BBY. The Revanchists, a group of Jedi advocating for the Republic's defense in the war, journeyed to Cathar seeking evidence of Mandalorian atrocities. The Jedi Council, having recently addressed another faction of rogue Jedi, dispatched a team of loyal Jedi, led by Council member Vrook Lamar, to confront them and demand their disbandment. Shortly thereafter, the leader of the Revanchists discovered a discarded Mandalorian mask. Following this discovery, all Jedi present experienced a vision of the battle, confirming the near annihilation of the Cathar by the Mandalorians. Overwhelmed by what he had witnessed, the leader of the Revanchists, who adopted the name Revan, vowed to relentlessly pursue the Mandalorians' defeat. Awareness of the battle served as the turning point, convincing many Jedi to join Revan's cause. Meanwhile, the Council sanctioned the Revanchists' actions but continued to discourage other Jedi from joining their ranks.
The events of the battle were first portrayed in flashback in issue forty-two of the comic book series Star Wars: Knights of the Old Republic, released in 2009 and set "approximately 3,963 years before the Battle of Yavin." In the story, Ferroh mentions in the present, "When I returned, a dozen years ago, my people had simply vanished." Based on the story's timeframe and Ferroh's statement, his return to Cathar occurred around 3975 BBY, placing the Battle of Cathar in or before that year. However, the earlier 2008 roleplaying game guidebook Knights of the Old Republic Campaign Guide dated the event to 3973 BBY, as did the subsequent 2012 reference book The Essential Guide to Warfare. This article uses the most commonly cited date.