Unidentified Outer Rim battle

At some point during the Reconquest of the Rim portion of the Imperial Period conflicts between 19 BBY and 17 BBY, a battle occurred somewhere within the Outer Rim region. It was known that the Imperial enforcer Darth Vader was personally involved in the conflict, and had managed to effectively persuade the Outer Rim region into joining the Galactic Empire as a result of the battle.