During the Second Galactic Civil War, the Mandalorians sided with the Jedi Coalition that opposed the Galactic Alliance government. In 41 ABY, the Mandalorians defended the planet Roche during the first Galactic Alliance assault on the world, and they later took part in the attack on the Moff Council during the Second Battle of Roche. In retaliation, Galactic Alliance Admiral Atoko was tasked with neutralizing the threat that the Mandalorians posed.
With the remnants of the Galactic Alliance Fifth Fleet, Atoko led the attack on the Mandalorian homeworld of Mandalore. Atoko released into Mandalore's atmosphere a nanovirus that had been developed during the Second Battle of Roche. The nanovirus targeted the Fett genome, with the intended result that the Mandalore Boba Fett and members of his family could never again set foot on the world.
The battle of Mandalore was first mentioned in Legacy of the Force: Invincible, the ninth and final novel in the Star Wars: Legacy of the Force series, written by Troy Denning and released on May 13, 2008.