Designated "Third of Five", he was a member of the Borg Collective and dispatched in a Borg scout vessel which crashed on a unnamed planetoid. He was the only survivor of the crash whereupon he was discovered by the crew of the USS Enterprise-D in 2368. They began to study him and with an attempt by Starfleet to use the drone to spread a virus into the Collective in the hopes that it would destroy Borg. However, the drone began to reassert its individuality after it had been cut off from the Collective whereupon Lieutenant Commander Geordi La Forge gave him the name Hugh. Ultimately, Captain Jean-Luc Picard allowed Hugh to return to the Borg with his newfound individuality rather than use him as a weapon. (TNG episode: "I, Borg")
However, rather than be reincorporated into the Borg Collective, Hugh's sense of individuality spread to his fellow drones. Sensing that his individuality had infected the vessel that had retrieved him, the Borg cut off their link to the vessel leaving it directionless and in a chaotic state. Rather than die from their newly-acquired status as individuals, Hugh and his fellow Borg were saved by the Android Lore who discovered their ship and saved them whereupon he established himself as their leader.
Despite what he had done, Hugh and a number of like-minded, liberated drones opposed Lore's leadership and separated from the main group. In 2370, his group lived in secret on a planet that the rogue Borg had made as their homeworld. At the same time, Lore had managed to capture and brainwash his "brother" Data and when the crew of the Enterprise came to the world looking for him, Hugh encountered a member of their away team. At first angry at their actions, he decided to work with the away team once he learnt that his friend Geordi La Forge had been captured by Lore and was being experimented on. Taking his faction, Hugh and the Starfleet team stormed Lore's fortress and helped in ending the mad android's plans. (TNG episode: "Descent")
When Hugh was recognized as a leader to the independent Borg, there were some such as Enab who split off from their fellow liberated drones and attempted to find a means to recover the unity of the hive mind. Enab's group began to attack Tholian in worlds in 2371 in an attempt to research the secret of their natural hive mind but he was stopped by the crew of Enterprise-D before his actions brought a war in the quadrant. (TNG comic: "Cry Havoc")
Hugh and a tribe of his comrades later established a homeworld on a planet belonging to the Borg Collective which served as a dumping ground for damaged drones. He along with a member of his faction, a female former drone called Miko, saved what drones they could. Helping them renounce their implants and nanoprobes, he helped give them a new reason for living. In 2373, after the destruction of the Borg Central Node by James T. Kirk, Hugh and his clan encountered a near dying Kirk. He helped teach Kirk several techniques designed to heal him after which he helped Hugh recover those Borg that survived the Node's destruction as well as freed them. (TOS novel: Avenger)
After this chain of events, Hugh helped form the Independent Nation of Borg consisting of all the Liberated individual Borg that were free from the hive mind. Due to his actions, he took on the title of Primary and thus became their leader. Hugh worked to ensure that his faction were recognized as being different from the Borg Collective but had little success in his goals. Thus, he led the Nation into retreating into the Delta Quadrant in order to avoid conflict as well as run a cover campaign to restore individuality to the other Borg drones that were enslaved to the Collective's will.
By circa 2374, he approached USS Voyager crewman and former Borg Seven of Nine and asked her to help him in his goal by her being the Nation's ambassador to the Federation as well as asking her to join his faction. Though she declined to join Hugh, she did agree to speak on his behalf when Voyager returned to Earth. (VOY short story: "Seventh Heaven")
At some point in 2380, Hugh and the Nation were attacked by a variant breed of Borg that had assimilated the Einstein. They managed to repel the invaders who fled and whilst they were not connected to the ships Borg, they did learn of its intention to assimilate the NGC 6281 entity. Hugh along with the Zero Rebekah Grabowski took Liberator to combat this threat whereupon he made contact with the crew of the USS Enterprise-E where he once again met Captain Picard. Agreeing to help him in stopping the Einstein, Hugh also asked the Starfleet crew to aid the Nation's ability to reproduce thus making them a true civilization. During the course of the crisis, Hugh sacrificed his own life to destroy the divergent breed of Borg on the Einstein by using the Liberator as bait allowing him the opportunity to board the assimilated vessel and deliver to it the multivector pathogen. Despite his death, enough of his genetic material was salvaged allowing for Grabowski to bear his child thus giving the Liberated the chance to continue as a true race. (TNG novel: Greater Than the Sum)
In an alternate timeline, Hugh and Seven negotiated a treaty between the Borg and the Federation in 2390 to fight the Bajoran Ascendancy and the Grigari during the War of the Prophets. (DS9 - Millennium novel: The War of the Prophets)