The Sirius Threat
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After the Anti-Earth Movement coalesced and delivered the 2682 Ultimatums to the Earth's Humanity Congress, the UEG government determined that the colony of Rondolina, in the Sirius Starzone, was the primary supporter of the Anti-Earth Movement, and thus the Earth's primary threat.
The United Earth Government began to wage a propaganda war against Sirius, claiming that Sirius was stirring up baseless anti-Earth sentiments in order to further an ambition of galactic domination. The campaign attempted to demonize Sirius by making them out to be power-hungry zealots, intent on supplanting Earth as the governing body of all mankind. The campaign was intended to derail the Anti-Earth Movement and redirect the building resentment of the colony worlds away from Earth toward Sirius.
Ironically, "The Sirius Threat" served the opposite goal: the campaign was so effective, it convinced many colonial citizens that Sirius had not only the will to stand up to the United Earth Government militarily, but also the means to do so. This helped to unite the Anti-Earth Movement against the UEG, leading to the formation of the United Colonial Army and, eventually, the outbreak of the Earth–Sirius War. (LOGH: 'To Earth')