Willham Burke was the Admiral of the Fourth Battle Fleet of the Rebel Alliance, operating in the Outer Rim. He later served as a commander in the New Republic's Third Fleet, winning numerous victories in the years immediately following the Battle of Endor.
He was considered a very competent commander, and many Rebel pilots took it as a great honor to meet him. He was known to help train several pilot squadrons including Havoc Squadron, Vortex Squadron, Crimson Phoenix Squadron, as well as freelancers from CorSec and the Smugglers' Alliance. Soon after the Battle of Yavin he was known to be seen in a hotel in Doaba Guerfel on Corellia. While there, he assigned a single individual to battle against 30 Imperial starfighters near Kessel, and eventually a follow-up assault against an Imperial CR90 corvette.
In 5 ABY, Admiral Ackbar placed command of the New Republic Third Fleet temporarily in the hands of Admirals Burke and Kalback, who worked to sever the forces of Imperial warlord Treuten Teradoc from the Core Worlds. Leading the fleet from the Mon Calamari Star Cruisers Remember Alderaan and Justice, the pair bested the warlord's task force at Togoria and fought their way to the planet Lantillies on the Perlemian Trade Route, where they connected with the forces fielded by the planet Contruum. Having established a hold on the Perlemian, the two admirals headed in different directions; while Kalback headed for Corsin, Burke pressed Coreward, encountering the forces of Admiral Ledre Okins in the Chazwa system. The two engaged in a long series of feints and raids before Burke's trickery convinced Okins to send key ships to the Pindra system, where they were caught in a grav trap hidden in the system's careening asteroids. Burke was able to destroy Okins at the latter's base of operations in the Colla system.
In 6 ABY, Burke and General Brenn Tantor captured Reytha, Gyndine, and Commenor, placing him in position to move into the Core, along with Admiral Firmus Nantz of the First Fleet and Admiral Chel Dorat of the Fourth Fleet.