Gradius: The Interstellar Assault is the second portable game in the Gradius series, originally released in Japan for the Game Boy in 1992. It was released in 1991 in Japan as Nemesis II: Return of the Hero. It is also a sequel to the Gameboy game, Nemesis. Both games can be considered a spin-off of the main series, but unlike Salamander and Gradius Gaiden, they don't appear to be part of the official Gradius canon seen in Gradius Galaxies.