This attack matched the fleet of the Vallaido pirate clan against its longtime enemy, the Seville pirate clan. As the Sevilles were reinforced by Imperial starships, they were able to obliterate the Vallaidos.
The Seville pirate clan and the Vallaido pirate clan had been rival pirate organizations for many generations by the time of the Galactic Civil War. As their enmity was well-known, no-one was surprised when one clan's starship fleet attacked the other.
At that point, the Seville clan was led by Yearo Seville, who made a deal with the Galactic Empire. Under this alliance, the Seville fleet had Imperial starships as reinforcements. With this firepower, Seville attacked the Vallaido fleet. Overwhelmed, the Vallaido fleet was destroyed.
The man named Siro Simito, a former member of the Vallaido clan, was aghast when he discovered this. Simito then joined the anti-Imperial Alliance to Restore the Republic and began working as an undercover agent for General Airen Cracken.