Destruction of the SD Lucifer
The Destruction of the SD Lucifer was the culmination of the campaign against the Shivan intruders on 29 March 2335.
Aftermath of the Destruction of Vasuda Prime
Vasuda Prime was destroyed, and the Vasudans were leaving their homeworld, trying to find refuge anywhere they could. Escapees were sheltered at Sirius, Aldebaran and Beta Aquilae. Some even went as far as Altair.
Above Altair IV, some escape pods lost power and crashed to the surface. The curious Vasudans explored the area and found remnants of an unknown civilization, the Ancients. The Vasudans found "conclusive" evidence that the Ancients had been destroyed by Shivan weaponry (apparently noone in the GTA or PVE had noticed this years before, somehow).
The Lost Civilization
The downed Vasudans sent S.O.S. signals to the GTVA. They mentioned their findings and Galactic Command deployed additional ships to assist them.
A science vessel, the GTSC Rosetta, was sent to Altair with linguists on-board to help extract a collection of Ancient records. Transports arrived to take the linguists to the system safely. The systems between Altair and "Terran space" were being held by the Shivans, so military escort was necessary. The GTD Bastion sent three wings of fighters, equipped with the then-new intersystem jump drive, to Altair to escort the scientists.
The records were partially deciphered and were being moved back to Terran space. The Hammer of Light, knowing the importance of the records, did everything they could to destroy them. A Hammer of Light flagship, the PVD Anvil, was destroyed while attempting to stop the convoy from reaching Terran space. (See: Hammer of Light Rebellion)
The GTD Bastion was tasked with hunting down the SD Lucifer inside subspace. The Bastion was so far behind the Lucifer that only her fighter wings could catch up with the Shivan warship. In the subspace tunnel, the Terran-Vasudan fighters attacked the Lucifer and destroyed her five reactors. The destruction of the Lucifer inside the subspace vortex had an unforeseen side-effect: The jump tunnel collapsed and all contact with the Earth and the Sol system was severed.