The Galaxy Federation is the main protagonistic force of the Thunder Force series. An extraterrestrial superpower, the Federation is in constant war against the ORN Empire throughout the series.
The Federation is constantly struggling against a galactic war with the ORN Empire's large fleets, because of this, it seemed as though the ORN Empire has the upper hand. As a means to counter this disadvantage, the Galaxy Federation begins producing a line of starfighters known as the Fire LEO series under codename "Project Thunder Force". These fighters, though small in size compared to those of the ORN Empire, prove effective for taking out the ORN Empire's central power sources, including Khaos, the main antagonist of the series.
In Thunder Force V, a different perspective is taken in the series by showing what happens when mankind on the planet Earth discover the fourth Fire LEO model created by the said Federation. In response to the discovery, the humans begin producing its own series of technology, including a line of their own "starfighters" known as RVR, as well as a supercomputer known as Guardian; however, the latter of these goes rogue and begins attacking humankind with the said technology.
In Thunder Force VI, 10 years after a successful victory against the supercomputer from the previous installment, the ORN Empire tracks down Earth and begins an invasion against it. The humans uncover the remnants of the original spacecraft they had found and manage to encode a cry for help by the said Galaxy Federation. In doing so, they create a new refined RVR model capable of traveling into space without need of an extra weapon attachment, and then is able to join up with the Galaxy Federation, to which the two forces form an alliance in the hopes of defeating the ORN Empire once and for all.