Starfleet’s Ninth Fleet was intended to be part of Operation Return during the Dominion War but did not arrive in time. Following the recapture of Deep Space 9, the station was designated as headquarters of this fleet and General Martok was named its Supreme Commander.
Following the war in 2376, the Ninth Fleet was combined with the Romulan Twelfth Fleet to form Obsidian Fleet. After only one year, the Romulans pulled out of the operation, leaving Starfleet in sole control of the fleet. The Command Staff of the Ninth Fleet can be found here.
The Loki system is located on the edge of the Federation/Romulan Neutral Zone. Its radiation and constant solar activity had wreaked havoc on its sole populated planet, Obsidian.
In 2296, Starfleet, at the behest of the Federation Council, established a small outpost on the planet. Its primary mission was to help the planet’s population overcome the troubles caused by the degradation of its ozone layer.
It would be a lie to say the task was easy. The outpost was almost destroyed shortly after its completion; yet now, almost a hundred years later, the desert planet of Obsidian really does bloom. Its ozone layer has been repaired, and Federation terraforming teams are bringing life back to the planet.
The fact remains, however, that the planet lies on the very edge of Federation space, only .9 of a light year from the Romulan Neutral Zone.
In 2369, plans were put forward for the construction of a permanent starbase. It was passed, and construction began, only to be slowed a year later as the Dominion and Borg threats grew.
Construction was slow; the war with the Dominion was taking up the majority of the Federation and Starfleet’s resources. It was shortly after the war that the Romulans offered to make the starbase a joint venture. Starfleet accepted, and in 2376 the starbase, newly painted and named Starbase Obsidian, was completed. It was then that the reason for the Romulan co-operation became apparent: the Borg were attacking more and more regularly, ships were vanishing, and whole outposts went missing. In response, the Federation Council and the Senate created a joint fleet. The 9th Federation Fleet and the 12th Romulan Fleet were combined to create Obsidian Fleet, their orders to defend the Romulan/Federation borders from any and all outside threats.
The venture was not always easy. As the war ended, relations between the Federation and the Romulans cooled. The cooling was also evident in Obsidian Fleet, where tensions between Federation and Romulan elements grew. After only one year, the Romulan government pulled out of Obsidian Fleet, leaving Starfleet in control of the Fleet.
Obsidian Fleet continues to protect the Federation into 2389, keeping an eye out for new threats to the safety of the Federation.