Over its nine-year existence, Garm Bel Iblis's movement managed to assemble a considerable military force, encompassing both naval and ground units. By the time of the Raid on New Cov, Bel Iblis commanded a fleet that included six Dreadnaught-class heavy cruisers, among them the Peregrine and the Harrier. These vessels had previously belonged to the Katana fleet and were later acquired from the smuggler Captain Hoffner. Each of these six cruisers was staffed by a crew of two thousand soldiers, bringing the approximate total personnel of his naval forces to over twelve thousand.

The ground forces under Bel Iblis's command were outfitted with Golan Arms anti-infantry turrets, Speizoc Arms anti-vehicle turrets, and KAAC Freerunner assault vehicles. They also possessed the Gargantuan, a unique heavy assault vehicle that had been purloined from an Imperial testing facility. It's possible they also possessed a Kuat Drive Yards v-150 Planet Defender ion cannon, given the presence of a control panel for such a device within the command center of the Peregrine's Nest.

In that same year, Bail Organa perished when his homeworld, Alderaan, was destroyed by the Death Star. This left Bel Iblis as the remaining senior rebel with enough influence to challenge Mon Mothma. She had begun to accumulate increasing amounts of power, leading Bel Iblis to suspect that she would usurp Emperor Palpatine's position if they succeeded in overthrowing him. Bel Iblis remained with the Alliance for several months, enduring the loss of many friends and finding himself placed on an Imperial wanted list.

Sometime afterward, Mothma authorized a Rebel Alliance attack on an Imperial garrison located at Milvayne within the Gyrica system, without consulting Bel Iblis or any of her other military advisors. Before the attack could be launched, Bel Iblis confronted Mothma about her actions at an Alliance conference, urging her to postpone and reconsider the operation. Mothma disregarded his objections, prompting an enraged Bel Iblis to question her motives for ordering the attack, suggesting it was merely a power grab on her part. After a heated exchange of thinly veiled insults, Bel Iblis declared that none of his troops would participate in the attack. He believed that Mothma's intelligence was flawed, as his own sources indicated it was actually a heavily fortified Imperial Ubiqtorate base, which his forces would be unable to overcome. Due to his dissent, Mothma informed Bel Iblis that the Rebellion no longer required his services. He then departed the chamber in anger, taking his loyal followers, including Sena Leikvold Midanyl and another aide named Irenez, with him, effectively separating from the Alliance.

Operating from a mobile base called Peregrine's Nest, Bel Iblis and his rebels achieved several significant victories against the Galactic Empire. However, they were perceived as less principled compared to the Alliance. Their most notable achievement occurred in 2 ABY with a successful attack on the Ubiqtorate base situated on Tangrene. Bel Iblis deployed all five of the Dreadnaught-class heavy cruisers that his movement possessed at the time during the attack, and all five ships returned to Peregrine's Nest in the aftermath.