The Battle of Optera was the final fight in both the Sentinels Campaign and the REF Civil War.
Prelude to Battle[]
The Robotech Expeditionary Force general Thomas Riley Edwards had sided with The Invid Regent after his schemes were exposed and had taken Lynn Minmei captive. During the escape of Edwards' loyalists, the Ghost Squadron, proved devastating, thanks to their use of Shadow Technology. Edwards was onboard the newly finished cruiser Icarus, the Regent assisted him into escaping, partially destroying the REF's flagship, SDF-3.
Months later, a cruiser newly built, the Tokugawa, was finished sooner and sent to search Edwards, led by Vince Grant. About a year after Edward's evasion, the Tokugawa located them over Optera, the Invid homeworld.
Battle[]
A shoot from the Icarus Synchro Cannon crippled the Tokugawa. The Regent Carrier engaged the REF ship... and the Invid leader uncovered than Edwards used the Invid Brain to take full control of his forces. A boarding team of the REF, led by Breetai, boarded the Carrier, and they moved the ship to shield the Tokugawa from the Icarus. But that didn't stopped Edwards, which shoot anyway, killing both the Regent and Breetai, and blowing the Carrier. That allowed him to take full control of the Invid Regents army. The Tokugawa began falling to Optera. Meanwhile, the rebuild SDF-3 was already finished and the REF forces were provided with their own version of the Shadow Technology, developed thanks to the Haydonites' help.(Robotech: Prelude to the Shadow Chronicles 2: Retribution)
The SDF-3 received the Tokugawa's distress call. The Tokugawa's crew, falling to Optera, managed to evacuate the ship, with Vince being the last one, but before they can reach the ground, they were intercepted and captured by Invid forces under Edwards' control. After gathering all the prisoners in a former Invid hive, his new command post, Edwards explained to Grant his intentions, which included transforming all the REF prisoners which didn't join him into Invid monsters throwing them into a Genesis Pit. Edwards attempted to recruit Vince to his cause, but then was informed than the REF forces have landed and were engaging their men.(Robotech: Prelude to the Shadow Chronicles 3: Necessary Evil)
Admiral Hunter led personally the ground assault. In the air, his forces were crushing the Invid and Ghost Squadron, thanks to his Shadow Technology. When Edwards ordered his Invid to concentrate, Hunter made his cruisers to use his heavy weapons to annihilate them. When Hunter's forces reached Edwards, he unleashed a horde of Invid creatures exiting from the Genesis Pit. The general, distracted by the android Janice Em, which posed as Minmei, wasn't able to react. Janice informed Hunter about Edward's using the Invid Brain, and after firing at it, Janice, Edwards and the Brain fell to the pit. Without his leader, the last survivors of Ghost Squadron surrended.
But the battle was far from over: soon after, Edwards emerged from the Pit, turned into a gigantic monster combined with the Brain. He directed his Invid space units to attack the SDF-3, but Hunter ordered his people to evacuate. Janice, partially active, contacted Lisa, which commanded the SDF-3, to shoot at her position. The SDF-3's Synchro Cannons shoot at Edwards. Right before it was destroyed, Janice leaved her body and transferred her conscience to another one. The shoot destroyed Edwards, and without the Brain, all Invid units died. Hunter and the Tokugawa's crew escaped onboard the Icarus. The REF civil war was over.(Robotech: Prelude to the Shadow Chronicles 5: The Children of the Shadows)
Aftermath[]
The end of the conflict didn't weaken the REF too much, and apparently, left them stronger than ever: all the remaining Regent's forces were destroyed, and the only REF lost ship, the Tokugawa, was replaced by the Icarus. Besides, their forces were now much more advanced, with fighters and ships equipped with Shadow Technology and the Neutron-S missiles as ultimate weapon.
But the Haydonites, really, were manipulating the REF: all all their upgrades had trojan horses, which would be devastating for the humans during the Fourth Robotech War.(Robotech: The Shadow Chronicles)