My theory was that the original GTA was a military junta, with the grandfather of the Solar Republic's current Generalissimo as its head, but not with the sort of unrestricted power that the Solar Generalissimo has--he was "first among equals" in a council of military oligarchs. During the Great War, the GTA, unlike the Shivans, did not move their central government offworld. While the Vasudan emperor, his ministers, and the Parliament were evacuated when the Lucifer came, the GTA's ruling junta chose to stay on Earth in preparation for a last stand at Sol in case the Lucifer broke through. This meant that the GTA was essentially decapitated in winning the Great War, hence its rapid collapse as an interstellar empire. In Sol the period of chaos and strife was briefer than in the Terran diaspora, and the presence of a ruling Terran state was more or less continuous--there were rebellions and areas of temporary lawlessness, as well as lots of backstabbing, murdering, and chicanery going on in the transitional government, but no warlords carving out fiefdoms like in the diaspora. The first Generalissimo was quick to consolidate his power and his authority as the "legitimate" successor to the original GTA government. He eliminated his political opposition through various covert and overt means and rallied most of the GTA's remaining forces to his banner. Once he had secured his control over Sol, he renamed the state the "Free Democratic Solar Republic" and ruled as a totalitarian dictator, and since then the mantle of Generalissimo has passed from father to son.
As for science and BP, there is nothing scientific for that UEF "faith and reason" speech that follows Bei's near-death experience. If anything, it was anti-scientific.
