Bruce Wayne joined the League of Shadows to seek the means to fight injustice. He was still traumatized by the murder of his parents during the Gotham depression but had learned to give up on the idea of revenge. While traveling the globe, he was recruited from a Bhutanese prison by a man calling himself "Ducard", who saw great potential in the angry young man. During the final test in his training, Bruce was asked to act as an executioner and learned what the League really was about, that their leader wanted him to lead a mission to destroy the city of Bruce's birth. Bruce then destroyed their base and left the man he believed to be Ra's al Ghul to die there. However, he saved Ducard, his teacher while in the League.
Over seven years after his disappearance from the city, Bruce returned to Gotham and planned to root out its criminality and the corrupt. He became Batman to enact this plan, and used Ducard's lessons in the martial arts, stealth, intimidation, and theatricality. Meanwhile, the League was busy bringing a fear toxin (created from a hallucinogenic blue flower grown near their Himalayan base) into Gotham by employing some of Gotham's criminals, most notably Carmine Falcone and The Scarecrow. After Batman put both men behind bars, the League was forced to act sooner than expected and Ducard revealed to Bruce that he was Ra's al Ghul. Using a microwave emitter stolen from Wayne Enterprises, they began vaporizing the city's water supply, which the toxin had contaminated. Everyone who breathed in the toxin turned on each other in blind panic.
Batman, with the help of James Gordon, was able to stop the League before it could vaporize all the water in the city. In the process, Batman left Ra's for dead on a train that crashed, causing him to perish in the crash and resulting explosion.
The Dark Knight Rises
Following the death of Ra's al Ghul for which she blamed Bruce Wayne, Talia forgave her father and attempted to bring justice over his death and finish her father's work with the aid of Bane, who had become known as a mercenary with a rumored reputation following his excommunication from the League. Talia posed as Miranda Tate and came to Gotham, and became a shareholder and board member of Wayne Enterprises to fund the creation of a nuclear fusion reactor for which Bane abducted Doctor Pavel to turn into a nuclear bomb years later.
Batman asked Selina Kyle to take him to Bane after Bruce lost his fortune due to the risky trades made during the League's attack on the Gotham Stock Exchange so that Talia could takeover Wayne Enterprises and the reactor. In Bane's sewer lair underneath Gotham, Batman was challenged to a fight by Bane, wherein he outlined his aim of fulfilling Ra's al Ghul's destiny by destroying Gotham. Bruce was sent to the Pit after his defeat so that he could see it unfold and suffer.
The League of Shadows employed Gotham's older orphans to work in the sewers, as well as John Daggett's construction crews to pour explosive cement throughout the city that was later detonated. The city was held hostage as Bane posed as its liberator in a false revolution. The ranks of the League of Shadows were augmented as former Blackgate prisoners and others joined their army. Talia continued to use her false persona to undermine Batman's allies in various ways such as alerting Bane of a meeting with U.S. Special Forces within the city and misleading Gordon's group of cops into believing that a decoy truck was the one containing the nuclear bomb.
After Batman's return, Talia revealed herself to him and unsuccessfully used her trigger to detonate the bomb and left city hall to ensure its detonation. Bane was shot dead by Selina on the Batpod, and Batman fired on Talia's bomb truck in his aerial vehicle the Bat and led it to crash where she drew her last breaths, confident her plan for the nuclear annihilation of Gotham was unstoppable. The other members of the League of Shadows in the city were killed or captured by the GCPD. Batman saved the city by sending the bomb far away from Gotham over the water where it detonated.