The Battle of Annamar was a battle between the Galactic Empire and the Rebel Alliance in 3 ABY to stop the Rebellion's guerrilla tactics on Imperial cargo ships near the planetoid Annamar.
With their base hidden within an asteroid field, the Rebels made continuous attacks on Imperial ships. Wolf Squadron's successful attacks took ships and weapons from the Empire which were later used directly against the Empire.
In 3 ABY, the squadron was able to steal an Imperial convoy ship carrying a vital piece of the Death Star II's weapons system. After Wolf Squadron stole the piece of the Death Star, the Empire sent multiple ships into the asteroid field to recapture the ship and the stolen unit, but no Imperial ships ever returned from the mission.
Realizing that only the best pilot in the Empire could successfully retake the stolen part, the Emperor commanded Darth Vader to lead the mission to retrieve the unit. Upon reaching the asteroid field, Vader noticed a ship entering the field. Aboard was smuggler Luca on whom Vader used Force persuasion to retrieve information about his missions and the Rebel base.
After receiving the details about the Rebel base from Luca, Vader used Luca's ship, the Faithless, to lead a squadron of Imperial fighters to destroy the Rebel base. Luca provided the necessary codes to avoid and destroy the Rebels' cannons in the asteroid field. As the squadron came upon Annamar, however, Luca lied to Vader about the base's outer defenses surrounding the planetoid. The Empire's starfighters were destroyed in the ambush and the Faithless was forced to crash land on Annamar.
Vader forced Luca to take him to the Rebel base and later threw him aside once he had reached the base. Single-handedly, Vader destroyed the preliminary defenses of the Rebel base and, using the Force to levitate and drop a fully armed BTL Y-wing bomber, managed to annihilate the entirety of the Rebel base and Wolf Squadron.
The only survivor of the destruction was Luca, whom Vader spared as a method of proving that he still maintained a will of his own. With his mission accomplished, Vader left Luca alone on the planetoid and then returned to his ship the Executor to await new orders from the Emperor.