Unknown to most of the characters outside of her own race, Delenn was part of the Gray Council, the ruling body of the government of Minbar. Originally there were three members from each of the three castes: Worker, Warrior, and Religious. Note that the number three has significance in their culture.
When the Minbari first encountered humans, their culture and warrior code required them to approach with gunports open. This was misinterpreted as an act of aggression and the humans opened fire. Delenn was on board the heavily damaged flagship as the aide to a member of the Gray Council, and when he was killed he named her his successor. Delenn's first act was to cast the deciding vote to start the Earth-Minbari War.
Eventually the Minbari's advanced weaponry proved to be too much, and the final battle surrounding Earth had Delenn on a cruiser with the Gray Council to oversee the final battle. They randomly brought a human on board, which turned out to be the man who would take over Babylon 5, Captain Jeffrey Sinclair. The Minbari discovered that the souls of the Minbari were intermixed with human DNA. Minbari do not kill Minbari, so they immediately surrendered on the verge of victory.
All of this set up a grand sweeping story arc for the Minbari on Babylon 5. In the end, Delenn marries Sinclair's successor, grows hair, helps to lead the Rangers, is instrumental in the Shadow Wars, and remains a good example of a strong female character.
Iron Noder 2017