Following an Imperial triumph within the Sagma system, an Imperial armada under the leadership of Admiral Wullf Yularen as well as Captain Bannidge Holt laid siege to the world of Zygerria during 18 BBY. This Imperial force included Invincible-class Dreadnaught Heavy Cruisers—originally created for the administration of the Corporate Sector region—alongside a number of Venator-class Star Destroyers carrying wings of TIE/LN starfighters. The siege formed a component of the Listehol Campaign, which was an Imperial offensive against hyperspace lanes like the Listehol Run and also the Shaltin Tunnels in order to eliminate Zygerrian and Tervig enslavers, who received assistance from Sikurdian buccaneers operating in that sector. The blockade concluded when the indigenous Zygerrians brokered a truce with an Imperial Advisor that came accompanied by stormtrooper reinforcements. Following the siege, the Imperials launched a series of incursions targeting the planet Tervissis.
The siege initially appeared within The Essential Guide to Warfare, a comprehensive compendium focused on armed conflicts across the galaxy, authored by Jason Fry and Paul R. Urquhart, and was published in 2012.