Prior to his time in the Resistance, Li had spent time working in Terok Nor's Ore processing center.
Later, Li was part of a minor resistance cell. While the group was in hiding in the mountains, they were without food and power cells for their weapons and were forced down into the valley. Li was sent ahead to scout where he encountered Gul Zarale. When the other members of Li's group found the pair moments later; they believed that Li had killed the Cardassian officer in an intense duel, however the story wasn't quite true. In the actual event, he stumbled upon Zarale in his underwear, bathing in a river. The Cardassian was stunned and didn't react immediately and only when Zarale reached for his rifle, Li realized he still had his own phaser and fired at the Cardassian, killing him. Li didn't want to be a hero for doing such a thing but when he was discovered standing over the body and even after he tried to explain what had happened; no one believed him. Indeed, as Li and his follow resistance fighters travelled around, word of Li's exploits spread and grew to mythic proportions.
Li Nalas' career as a resistance fighter ended with his capture in 2360. Although his body was never found, he was presumed dead until 2370, when he was rescued from the Hutet labor camp on Cardassia IV by Major Kira Nerys of the Bajoran Militia and Miles O'Brien who posed as prostitute and her pimp, respectively, to gain access to the camp.
After he and his fellow prisoners were rescued, Li was taken to Deep Space 9 where he was immediately recognized. He was very uncomfortable with his status as a hero and attempted to secretly leave the station for the Gamma Quadrant. Discovered by the crew of the departing ship, he was returned to Commander Benjamin Sisko. After Sisko questioned Li and pressed him for an explanation, he admitted that the stories of his heroism were largely based on myth. Li told the Commander the truth behind the myth that surrounded his reputation. As Li would relate to Sisko, he would never forget the embarassed look on the Cardassian officer's face as he died in his underwear. Li confided with Sisko that he had always felt uncomfortable with being an accidental hero. Sisko confronted Li with the unfortunate truth that Bajor needed a symbol; someone that the people could beleive in because the planet was on the verge of civil war.
Shortly after his return to Bajor, Li was given both the title of Navarch and Kira's position as Bajoran liaison officer on board Deep Space 9, much to his embarrassment. Li assured the Commander that he would do his best to fufill his duties but that he could never replace Kira. This was done by Minister Jaro, who wanted to get Kira out of a position of power and to get Li off Bajor so that he would not influence Jaro's plot to take over the government.
His rescue proved to be just in the nick of time, as he was able to play a pivotal role in preventing a disastrous coup d'état orchestrated by the Alliance for Global Unity. He helped rescue Kira from the insurgents, and helped defend the station against General Krim's troops, who attempted to take the station by force. After capturing Krim, Li was able to explain that the coup was being orchestrated by the Cardassians. Krim told his troops to stand down. Li was killed while saving Sisko from a phaser attack by Colonel Day Kannu, and as a result, became a hero both in legend and reality.