Source: Wikipedia, "Galaxy Force (arcade game)", available under the CC-BY-SA License.
Galaxy Force (ギャラクシーフォース?) is a sprite-scaling rail shooter arcade game, released by Sega in 1988 and built upon the Sega Y Board. The game which is in the tradition of Sega's successful Space Harrier is set in space.
"In this distant Galaxy exist many systems harboring life. Trade and communication have arisen between these star systems, as has a great, dark force threatening these distant civilizations. To fight this dark menace the Space Federation was formed, but has met with little success.
The enemy calls itself THE FOURTH EMPIRE and has now attacked JUNOS, jewel of the Galaxy. The JUNOS star system, once so beautiful... is only ashes now. And on these ashes THE FOURTH EMPIRE is building the strongest fortress of all time, from which to complete their conquest of the galaxy.
The Space Federation must end this evil menace! Thus is launched Galaxy Force, to strike a hammer blow against the forces threatening civilization. Fortunately, having done this duty of saving JUNOS people and destroying THE FOURTH EMPIRE, a combatant of Galaxy Force returned to the ship."