Barell's operation on Geonosis was first mentioned in the novel Aftermath, which was written by Chuck Wendig and released on September 4th, 2015.
The idea of a post-Endor remnant grouping of Imperial forces attempting to restart the droid factories on Geonosis was seen in the non-canon series LEGO Star Wars: Droid Tales. In the series, General Maximilian Veers and the few stormtroopers under his command trick General Landonis Balthazar Calrissian into helping their efforts, only for the rebels to crush their operation.
Barell's operation on Geonosis was first mentioned in the novel Aftermath, which was written by Chuck Wendig and released on September 4th, 2015.
The idea of a post-Endor remnant grouping of Imperial forces attempting to restart the droid factories on Geonosis was seen in the non-canon series LEGO Star Wars: Droid Tales. In the series, General Maximilian Veers and the few stormtroopers under his command trick General Landonis Balthazar Calrissian into helping their efforts, only for the rebels to crush their operation.