Aamir Khan plays Mangal Pandey, who is one of the iconic figures in the First War of Independence (or the Sepoy Mutiny, if you prefer the British version). Very little is known of him.
British accounts of his actions indicate that he merely had a bad day at work. Apparently, he shot his officer, injured another and then tried to commit suicide. A plight that many present day officegoers afflicted with pointy-haired bosses no doubt identify with.
I don't think that this reading of history is correct. It ignores the societal conditions and the support that the rebellion got. These things don't happen in a vacuum. The East India company though its many actions had managed to rile up the population, the princes and the army. One of the proximate causes was that the new cartridges for the rifles was coated with the grease of pig and cow fat. Since the army consisted of high-caste hindus and muslims, this managed to offend both their sensibilities. Some officers
In any case, Mangal Pandey's actions were one of the earliest incidents of the War of 1857. The Army of Bengal of the British East India company revolted. Many princes joined the revolt. They managed to take over Delhi and installed Bahadur Shah Zafar, the last Mughal King, as the ruler. The British were initially taken aback by the sudden turn of events. They maanged to recover, and with the help of fresh regiments from Britain and other native regiments who had stayed loyal managed to ultimately roll back the tide. While it lasted, the war was a bloody and cruel affair. At the end of the War, the British government took over the direct rule of India from the East India Company.
The movie has tried to stay as close as possible to historic events. Not much is known of Mangal Pandey, so they have given him a back story. They have created a fictional character called William Gordon who is saved by Mangal in Afghanistan and becomes his friend. When the issue of greased cartridges comes up in Mangal's regiment, Gordon is told by his superiors that there is no animal fat in the cartridges and he announces that to his regiment. Mangal volunteers to fire the gun so that his friend will not lose face. Later, when it becomes clear that the cartridges did have animal fat on them, it creates a rift in their friendship.
I really liked the way that the character of William Gordon was developed and played. The easy camaraderie between him and Mangal(including a wrestling match at the akhara), his personal distrust of the company, his basic decency(he rescues a girl from sati) and his anguish at having unknowingly betrayed his friend are all portrayed very well.
Aamir Khan plays Mangal well. I really wish they had spent some more time developing his character rather than wasting time with two pointless songs. One was an 'item' number and another a 'holi' song. As it happens, one day Mangal is a sepoy in a regiment, and the next, he becomes a leader of the revolt chatting up Azimullah and Tatya Tope.
Azimullah is an interesting character. He was the prime minister to Nana Sahib, an Indian ruler. When the British East India company refused Nana Sahib succession under the Doctrine of Lapse, he sent Azimullah to Britain to plead his case. Azimullah was fluent in English and apparently something of a charmer. But he failed his mission. On the way back, he came via Constantinople and visited the site of the Crimean War. He observed that the British were not invincible and were currently taking a beating. He was one of the instigators of the War since he wanted to strike while the British were still recovering. Of course, none of this is shown in the movie, probably to save time to show the stupid Holi song.
Rani Mukherji plays Aamir Khan's love interest and is basically wasted in that role. I didn't think that love story was needed. I found the romance between William Gordon and Jwala (the girl he rescues) to be much more interesting.
The movie has played a lot of attention to recreating history and have largely succeeded. The period costumes and architecture look great. They have also used stories about the revolt intelligently (lower caste sweeper mocking soldiers for biting greased cartridges, prostitutes mocking soldiers for being slaves of the british, Gordon saying 'If you have a tradition of burning widows, I have a tradition of killing murderers'(this is a paraphrase of the quotes attributed to Lord Napier in the same context) ), if a little out of context. They have also taken liberties with the stories and characters, but I thought that was perfectly ok.
There are also interesting devices they have used to move the story along. Like there are these bunch of guys who hang around, smoke hookas and talk and they are used to tell us stuff like how the British have intrduced Telegraph. Gordon talks about how the East India Company is buying opium in India and selling it in China (which caused the Opium Wars, where the Indian sepys fought). The caste system prevalent at that time is shown as is an attempted Sati. These go a long way towards providing some depth for the movie.
In all, I liked the movie. They have basically made a historical movie while still abiding by the bollywood formula. I wish they had freed themselves of that adherence, but that's just me.