The film is set in China in the 1860s, during the Taiping Rebellion. It is based on the assassination of Ma Xinyi in 1870. In the beginning, there is a battle between loyalists and rebels, during which all of the loyalists are killed except Qingyun, the general. Qingyun goes to a village nearby where the inhabitants engage in banditry, being led by two men, Erhu and Wuyang. He offers his assistance in executing a raid against a rebel convoy. However, a loyalist army assaults the village shortly afterward and seizes the spoils for themselves. Around this time, Qingyun begins an affair with Erhu's wife.
Since the villagers are poor and starving, Qingyun convinces them to fight the rebels as an independent loyalist war-band. Erhu and Wuyang are distrustful of Qingyun, so the three of them perform a blood oath where, under the pain of death, they promise to care for each other like brothers. The war-band wins a series of victories. Qingyun becomes ambitious and prepares to attack Suzhou and Nanjing. However, the government becomes fearful of Qingyun's growing influence, and decides to deny reinforcements and provisions. As a result, the attack on Suzhou becomes a year-long siege.
Erhu attempts to kill the enemy commander by sneaking into the city in disguise. He is quickly captured, but to his surprise, the enemy commander was already planning on surrendering, and allows Erhu to kill him in exchange for sparing his troops from execution. However, Qingyun refuses to honor the deal due to a lack of food and manpower to keep them prisoner. Qingyun temporarily detains Erhu to keep him from interfering. Afterwards, he has the prisoners locked in the palace courtyard and massacred with arrows from atop the walls. Embittered, Erhu considers desertion, but Qingyun convinces him that the attack on Nanjing will liberate millions of innocent lives.
Nanjing is easily taken, and Qingyun, in return for his grand success, is awarded the position of Nanjing's governor. As Qingyun waits for his inauguration, he tries to make friends with other upper-class people. Erhu, however, has been jaded by the war, and does improper things such as handing out bonus pay without permission. Qingyun responds by arranging for Erhu's assassination, fearing a loss of reputation with the upper-class. Erhu, as he dies, curses the name of a rival, not realizing that he was betrayed by his own brother.
Wuyang, having discovered Qingyun's betrayal and Qingyun's affair with Erhu's wife, reacts by killing Erhu's wife. On the day of the inauguration, Wuyang jumps out to kill Qingyun, but is unable to defeat him. It is then revealed, through a flash-back, that Qingyun's promotion was fake, and that the government's real desire was to murder Qingyun for gaining too much influence. At this point, a government soldier appears behind Qingyun on a rooftop and shoots him in the back. Realizing he has been betrayed, a mortally wounded Qingyun allows Wuyang to fulfill their blood oath by killing him. The government then frames Wuyang for the murder and gets ready to execute him. The film closes with Wuyang observing that "Dying is easy. Living is harder."Jet Li as Pang Qingyun
Andy Lau as Zhao Erhu
Takeshi Kaneshiro as Jiang Wuyang
Xu Jinglei as Liansheng
The film was originally titled The Blood Brothers (simplified Chinese: 刺马; traditional Chinese: 刺馬). Director Peter Chan said it was influenced by the late Chang Cheh's 1973 film The Blood Brothers, which is itself based on a famous high profile assassination of a local governor in 1870, but denied that it is a remake. He also decided to change the title to The Warlords in order to avoid confusion. (Note that there is another Chinese film with the English title Blood Brothers released in mid-2007.)
When asked why he chose to move away from his familiar turf of romance films, Chan said that The Warlords is actually not a martial arts film at its heart, though it contains elements of the martial arts. He added that he had made a wish to make a film depicting men's affections after watching John Woo's 1986 film A Better Tomorrow over twenty years ago, and has now finally gotten the chance. His goal is thus to "lead [his] audience to reclaim [the same kind of passion]" as in A Better Tomorrow, which he said is lacking in recent films.
Shooting began in early December 2006 in Beijing. Many outdoor scenes were shot in Beijing, Shanghai and the town of Hengdian in Zhejiang province.
The film ran into copyright troubles on 19 March 2007 when Chinese artist Wang Kewei filed a lawsuit against the film company for using his work in the promotional artworks without his consent. Wang claimed that in a short promotional video shown during a press conference held on 11 December 2006 in Beijing, the film company used ten pieces of his work with minor alterations. The film company has not given an official response.
Production of The Warlords officially wrapped up on 28 March 2007. Post-production work was divided among Hong Kong, Los Angeles and Bangkok.
Jet Li received US$15 million, while Andy Lau received US$6 million and Takeshi Kaneshiro received US$2 million for the film. The film had a budget of US$40 million. The producers explained the huge salary for Li (over a third of the film's budget) by saying Li's participation ensures an international distribution for the film.
In IMDB the film has received a rather positive review of 70% by over 17 000 film critics and viewers.
The film won many prizes in many Hong Kong, Chinese, Asian and international film festivals in 2008-2009.
In Rotten Tomatoes the film has an aggregated score of 65% based on 51 reviews.
Perry Lam of Muse has also given the film a generally positive review, praising it for taking 'a clear-eyed but sympathetic look at its flawed heroes'.