The Third Alien War
Mere days after the base is raised to operational status, several unregistered contacts appear in scanning range, passing through the Frontier. The unknowns are intercepted by an X-COM craft, which is fired on. A full X-COM squadron then launches, intercepting and destroying the UFOs. The materials are taken back to base, where Earth science teams confirm that they correspond to alien materials from the first war.
Over the following weeks, a number of outposts throughout the Frontier are assaulted by the alien forces. X-COM successfully defends many of the outposts, and begins to despatch probes to investigate the Frontier. Several alien bases are discovered within the Frontier, and are rapidly destroyed. Alien technology has not progressed much since the first war, so despite their superior numbers X-COM wins many battles.
It becomes apparent to X-COM that the Frontier is not the home space of the aliens after all; they too have only recently begun colonisation efforts. In September, a message is intercepted from the alien commanders - X-COM technicians decipher it to discover the horrifying news that the aliens are steadily constructing a vast battleship. The warship possesses a weapon that is capable of destroying Earth with a single blast. Extensive scanning of the Frontier, however, reveals no signs of construction on such a scale.
2068
X-COM scanning reveals that large numbers of alien craft are apparently disappearing near the only "black hole" in the Frontier. It is theorised that they must be disposing of huge quantities of waste materials this way - or perhaps that they are capable of resisting the brutal gravitational forces of the black hole. One of the GSC's wilder theories is that black holes may lead into other dimensions, and X-COM command leaps on the idea, realising that the alien battleship might be under construction on the other side of the black hole.
Research into alien technologies reveal great secrets, but it is a human breakthrough by the GSC that astonishes most. Nuclear fusion weapons, hydrogen bombs and more - all pale into insignificance before the newly developed Nova bomb. The bomb forces a star to prematurely go supernova, a process that destroys everything within a huge radius. The weapon terrifies all who know about it, and it is kept heavily under wraps. The only reason the technology is not hidden away altogether or even destroyed is that it might present a way of defeating the aliens.
Further research into captured alien vessels leads to the development of a drive system capable of propelling a starship through a black hole, harnessing the gravitational forces. The UGS MacArthur is drawn away from patrol duties to be fitted with the new drive, and within hours five newly developed Avenger II's are docked aboard her. The tiny fleet departs, passing through the black hole.
One incredibly tense hour later the MacArthur returns, bringing with it tales of victory. The star around which the alien battleship was orbiting has been destroyed, and with it the alien commanders in the Frontier. The remaining alien forces are once again rounded up and destroyed.
The third alien war is declared officially terminated.