Lenonn was one of very few Minbari who still studied and believed the Prophecies of Valen concerning the Anla Shok. According to Valen the Rangers were to be the eyes and ears of their people, watching for the Shadows to return after a thousand years when the Anla Shok would be ready and instrumental in fighting the next great war. Lenonn knew that the Rangers were not strong enough or prepared for this. Many Minbari including some on the Grey Council dismissed the Anla Shok with a contempt, feeling that the Warrior Caste alone should be responsible for protecting Minbar. The Caste Elders rejected Lenonn’s pleas for recruitment, funds and larger facilities to build the Rangers into readiness, saying that there were too few of them to justify the expense.

In desperation Lenonn demanded a meeting with the Grey Council, as was his right as leader of the Rangers. Taken aboard their ship he pled his case before the Nine. The result was Dukhat’s decision, as supreme leader of the Minbari, that the Grey Council should go to Z’Ha’Dum to see if the Shadows had returned to their old world, proving the danger that Lenonn feared. It was in the course of this journey that they encountered the Earth ship Prometheus which, believing themselves to be in danger, opened fire on the Minbari. Dukhat was killed, and the resulting anger among the Minbari led to the beginning of the Earth-Minbari War..

Lenonn remained with the Minbari Fleet as the war progressed. Dukhat had confided much in Lenonn, for it was he who arranged for Dukhat’s possessions to be brought aboard the Grey Council warship and his sanctum recreated in every detail. And it was Lenonn who sent Satai Delenn to the sanctum to encounter the Vorlons for the first time. In keeping with Prophecy, Vorlons had been secretly in contact with Dukhat for some time and Delenn was told that they were "creating the future". The two Vorlons showed Delenn a holographic image of Dukhat whose message to her was that Humans were to be the key allies in the coming Shadow War and she should work together with the Vorlons to find them. Lenonn confirmed that this was true and that this was why the present war must be stopped.

At Delenn’s request Lenonn agreed to be a secret mediator between the Minbari and Earth in an attempt to bring about peace. As a Ranger he could act independently. Delenn as a member of the Grey Council could not. Lenonn welcomed this chance because he had feared that at his age he would never again have the opportunity to serve his people as a Ranger should. The Narn, working as liaison between Earth and Minbar, set up a secret meeting in an abandoned bunker on a remote planet. Lenonn rapidly acquired a basic knowledge of Human language for this meeting.

On the planet Lenonn met with Commander John Sheridan, a war hero who had recently destroyed the Minbari Black Star, Dr. Stephen Franklin who had some previous knowledge of the Minbari, and the Narn G’Kar who had accompanied them as translator. Before they could open negotiations the Centauri, believing the meeting to be a secret Narn/Earth arms deal, destroyed the ship which had transported the Earth delegation, and the bunker was bombed. Lenonn, mortally injured, realized that when he did not return the Minbari would come to look for him. On finding Earth officers with his body the Minbari would blame the Humans and the war would grow worse. With his dying breath he told Commander Sheridan to listen carefully and repeat what he said exactly.

Lenonn’s body was returned to the Grey Council ship and Satai Delenn. The Humans were about to be taken away for execution when Sheridan urgently repeated Lenonn’s words. He knew what was in Dukhat’s sacred place: "Isil-zha" – the future. Delenn realized that this must be a message from Lenonn as only he and she knew of the presence of the Vorlons. Lenonn was telling her to trust them as part of the future they were trying to create. She let the Humans go.