On the topic of the UEF holding the Sol note. Possible reasons for the GTVA not being able to hold the node on the Sol side:
* A sudden Shivan invasion in GTVA territory, as defenses are having a hard time, the Sol battlegroups are recalled.
* Vasudans interfere in political affairs and the GTVA is pressured into removing it's forces from Sol.
* The public image of the GTVA war effort changes, possibly through information of the wars nature leaking (source possibly sympathisers, perhaps Anita Lopez blowing the whistle), politics pressure the GTVA into a treaty.
* Vishans suddenly interfere and change the balance into the UEF's favour.
* A new weapon is employed, it proofs efficient against the GTVA, forcing the latter to retreat.
* A secret unannounced fleet, something wack like a Feyadeen owned fourth Solaris with significant escorts joins the UEF ranks and tops the balance, through a blitzkrieg. Essentially plausible deniability, denying the existence of another Solaris and fleet, by openly lying to the UEF media network while holding up the pretense of a 100% open information policy.
* While holding their lines, the UEF pressures the GTVA by actively destroying hard-needed resources. The GTVA ends the war and calls for a treaty to still try and get those needed resources: possibly by signing a treaty where officially the UEF is subjugated (to hold up the ruse of GTVA victory to it's citizens), but where unofficially and in reality, the UEF decides the terms of the treaty and stays autonomous in the Sol system.