And so the Republic quakes in uncertainty as we take our foothold in the Core!
—Darth Callidus in his speech to a gathering of Imperial Military members.
The Invasion of Corellia was an important battle in the Second Galactic War that led up to the Battle of Corellia and was started under the command of Darth Decimus, Darth Callidus led the Imperial Navy in the neutralization of Republic and Rogue Corellian Vessels with minimal casualties, while Darth Charnus led the Vanguard of the ground invasion on the planet Corellia in preparation for their Master's arrival to lead the campaign personally.
Soon enough Corellia would become a military and political boiling point as countless forces divided between Imperial and Republic allegiance arrived on Corellia in order to win over the planet, some on their own agenda and some for their own profit. Upon noticing that the Republic and Jedi were in a position to make an attack on the Sith homeland Callidus and his Flagship were withdrawn by command of Darth Marr to lead the First Defense Fleet before the Battle of Corellia could officially happen.