Ginga Eiyuu Densetsu Gaiden

The story is staged in the distant future within our own Milky Way Galaxy, approximately in the 35th century. Unlike other science fiction stories, there are no alien civilizations. A portion of the galaxy is filled with terraformed worlds inhabited by interstellar traveling human beings. For 150 years two mighty space powers have intermittently warred with each other: the Galactic Empire and the Free Planets Alliance.

(Source: Wikipedia)