The Galactic Security Council was formed in the wake of the formation of the Sith Empire by Darth Voracis/Ken Palpatine, it's purpose was to coordinate the war effort against the Sith. A secondary objective of the Council was to mend the rifts that opened between the governments, especially the Alliance & Empire, in order to unite Galactic Government once again, as had been instituted by the Second Corellian Treaty.