The engagement known as the Arda-2 assault occurred during the Galactic Civil War, taking place in the space surrounding the planet Arda-2.
According to the StarWars.com piece titled "Time Capsule: Darth Vader 1980", the T-65 X-wing starfighter group commanded by Luke Skywalker in this particular conflict was designated "Blue Flight". This detail served to retcon the involvement of Blue Squadron in the aforementioned battle.