The Black Fleet Crisis was the local conflict in the Koornacht Cluster between 16–17 ABY that saw the New Republic intervene against the Yevethan Duskhan League in response to the xenocide of all non-Yevethan sentient life. The crisis was further defined by political upheaval within the New Republic.
When the Galactic Empire expanded into the Koornacht Cluster following the end of the Clone Wars, they discovered the Yevetha species and also noted the Yevetha’s rapid ability to learn new skills. The Imperials subjugated the Yevethan homeworld of N’zoth and its nearby star systems, built the Black Fifteen shipyards and put the Yevetha to work as skilled slave labor building, repairing and modifying vessels of the Imperial Navy.
About eight months after the Battle of Endor, the Imperial garrison at N’zoth was ordered to retreat and destroy the repair yard. Before they could initiate their withdrawal, an assault led by chief commando Nil Spaar took advantage of the Empire’s view of the Yevetha as mindless labor and seized control of the vessels undergoing repairs, the operational warships and the yards. All Imperials were killed.
Over the next decade and a half, the Yevetha developed their technical capabilities, developed advanced technologies in the form of starship shielding, gravity bombs, Aramadia-class thrustships and D-type fighters. They established the Duskhan League, which grew to encompass thirteen worlds.
In 16 ABY, the Duskhan League came out of its isolation to engage the New Republic, which was enjoying a period of peace marked by increased member applications, economic prosperity and military innovation, as well as the development of a bloated and divided bureaucracy. A delegation led by now-Viceroy Nil Spaar arrived at Coruscant, supposedly to seek a peaceful coexistence. Given their xenophobia and view of all non-Yevethan species as ‘vermin’ however, it is more likely that they were there on a mission to sow confusion and disruption prior to their planned war of extermination.
Using the New Republic’s lack of intelligence on the Dushkan League and Senatorial political infighting to his advantage, Nil Spaar extended his negotiations with Chief of State Leia Organa Solo over a period of weeks. Pressured by military and intelligence advisors who sought answers, and potentially an ally against the Core Imperial strongholds, Organa Solo entered the discussions, only to find herself on the receiving end of a political plot to throw the New Republic into confusion. During this period he played into her empathy towards a species subjugated by the Empire, allowing him to cultivate assets on Coruscant.
Unfortunately (or fortunately perhaps for the Yevetha), the Commander of the Fifth Fleet, General A’baht had sent astrographic survey ships to the areas around that of the Dushkan League. The New Republic had lacked accurate Star Charts of the deep core areas formerly belonging to the Empire, a fact which had made the General uncomfortable in the Fifth Fleet’s search for the missing Black Fleet. The fleet itself, and the Prowler, were searching outside the space claimed by the League, but that did not stop a Yevethan warship from destroying the unarmed surveying ship, claiming it had violated their space.
Spaar used this as his opportunity to set off a series of political machinations that sowed confusion amongst the New Republic. First, he accused Organa Solo of «warmongering» and begged for the Yevetha to be left in peace. Weary of going to war, many New Republic citizens expressed outrage towards the Chief of State and several member worlds even went as far as submitting articles of withdrawal. With the diplomatic outcome a complete catastrophe, Leia ordered the Fifth Fleet to return from the Falax sector to Coruscant—leaving the Black Fleet now completely unhindered to carry out Spaar’s plans.