Through the travail of the ages, mankind thought that it was alone in the universe. That it alone was the sole dominant existence in the galaxy. In the year 2039, mankind learned just how dangerous that assumption would prove to be. A mysterious and formidable alien race known as the Tarsians appeared and dealt humanity its baptism by fire on a cosmic scale. It is now 2048, and the Earth has compiled an overwhelming amount of military resources in order to launch a counterattack against the alien aggressors that devastated the Martian expeditionary force.