The Grand Imperial Union was reportedly a splinter group of the old Galactic Empire, supposedly headed by Moff Tragg Brathis. The Duskhan League claimed it existed, but the New Republic dismissed this as mere Yevethan disinformation.
The Grand Imperial Union declared their backing of the Duskhan League's conflict with the New Republic during a Yevethan pirate transmission on HoloNet Channel 81. This announcement marked the initial awareness of the Grand Imperial Union among the New Republic's leadership. Since Brathis was also an unfamiliar figure, most Republic leaders decided that the Yevetha had simply invented the Grand Imperial Union for propaganda gains.