Many centuries (decades?) ago the planet Glorie was colonized by the by Solararian Federation. Humanity had recently been embroiled in n interstellar war, and to ensure that the human race was never wiped out in a similar conflict a series of far-reaching colonization missions were launched. Glorie was but one many such colony worlds. As contingency against possible invasion, a series of fully self contained underground arcologies were constructed to shelter the planet's population should the planet be attacked by an outside force. These shelter, or complexes as they were commonly referred to, were each named for a single letter of the Greek alphabet.
Within a few years (decades? centuries?) of the colony’s establishment, a fleet of unknown origin dropped out of hyperspace and proceeded to bombard the surface. The planet's population was evacuated to the Complexes, distress calls were sent to nearby colonies, and the Auxiliary Computer Network was brought online.
The Strategic Armored Corps mounted a valiant defense, but were eventually overwhelmed. Sigma, Beta, and Upsilon Complexes were overrun or otherwise destroyed, and the enemy forces settled in for a long occupation. During this period, the Primary and Auxiliary data nets were disrupted, isolating the complexes. Alpha Complex's Computer suffered a critical malfunction and its primary memory was overridden by incorrect data files. The Computer, in absence of better information, and using the archaic data available, mistakenly identifies the aliens as "Commies". It assumes that the other complexes have been overrun by the commies, and that any humans form outside Alpha Complex must be commie sympathizers, and are thus potential threats.
After many years (months?) of biding their time, the people of Glorie reestablish contact between most of the complexes and the surviving SAC units. Over time, the Various Complexes have developed their own hierarchies and political factions, and efforts are undertaken to integrate them. Eventually, a federation of complexes is formed, with the idea that new planetary government will be created once the war is over.
The combined forces of the Complexes and SAC mount a highly moderately successful guerilla campaign. Alpha continues to remain isolated. Eventually, a relief force arrives, and engages the alien fleet. After several successful engagements, the Aliens are beaten back, and eventually the main body of their force retreats. War continues to rage sporadically across Glorie's surface, as pockets of Alien resistance stubbornly refuse to surrender. The people of Glorie emerge, and begin rebuilding. A few of the complexes, chief among them being Alpha, continue to remain in isolation...