The Sith armada, a fleet that predates the Galactic Civil War between the Galactic Empire and the Rebel Alliance, engaged the smaller Ghostfinder fleet in combat long ago. Although the Sith possessed a numerical advantage with their armada, they were ultimately defeated by the Ghostfinder fleet, which proved to be the superior force.
During the battle at Jakku in 5 ABY, when the Galactic Empire's naval forces clashed with the larger Defense Fleet of the New Republic, Fleet Admiral Gial Ackbar of the Republic recalled instances where smaller, weaker forces had triumphed. He reflected on the Ghostfinder fleet's victory over the Sith armada, as well as the Mandalorians' successes against the Galactic Republic.
The initial reference to the Sith armada within the new Star Wars canon occurred in the 2017 novel Aftermath: Empire's End, which concluded Star Wars: The Aftermath Trilogy by Chuck Wendig. Prior to this, various Sith armadas had already been established within the Star Wars Legends timeline.