The first two parts of Forster's A Passage to India are set in the fictional city of Chandrapore, India, with the third part taking place in Mau. While Forster doesn't specify a particular year, critics generally agree that the novel takes place at some point in the early decades of the 20th century while India was still a colony in the British Empire.
If you're unfamiliar with Indian history, reading the novel may feel a bit like eavesdropping on a conversation between strangers. Random words seem to be super loaded, and characters seem to get mad at each other over nothing. To get the subtext, it might help to have some knowledge of Indian history, so take a deep breath – we're going to try to get through three hundred years of Indian history in few paragraphs. (Here's a place to download some mood music.)
The British presence in India began in the 16th century, spurred by the market for tea, spices, and textiles. At the time, India was made up of independent, mainly Hindu states in central and southern India, and the Islamic Mughal Empire in the north. As trade increased, so did the British interest in establishing their holdings in India to maximize and eventually monopolize their trade with the region. This was done primarily through the British East India Company. But it wasn't until 1858 that Britain made India an official colony. British India, also called Anglo-India and the British Raj in the novel, consisted of areas that were administered directly by the British government (where fictional Chandrapore is located) and princely states that had a high degree of autonomy (where Mau is located, most likely the one in central India).
By the time we get to the events in the novel, the movement for Indian independence is gaining momentum, and it dominates the lives of the characters. While the novel takes place around the 1910s or 1920s, the Mutiny of 1857 casts a huge shadow over both the British and Indian characters. Simply uttering the word "mutiny" seems to inspire either intense hatred of Indians or intense nationalist feeling, depending on who is doing the uttering. The mutiny refers to an important moment in Indian nationalism. In 1857, sepoys, or Indian soldiers in the British military, staged a mutiny in Meerut, and the rebellion quickly spread across northwestern India. In the novel, Turton's villa is compared to Lucknow, where the British commissioner was assassinated by rebels (2.20.2). The mutiny was one of the factors that spurred Britain to formally establish India as a colony.
But the mutiny also inspired the Indian movement for independence. The deep divisions between the Muslims and the Hindus during the independence movement is revealed in the sometimes strained relationship between the Hindu and Muslim characters in the novel. The 1860s witnessed a Muslim revival and a renewed appreciation for Mughal culture and literature, which is evident in Aziz's deep love of Persian poetry and his nostalgia for the reign of the Mughal emperors.
In 1885, the Indian National Congress was founded initially to advocate for the rights of Indians within the British Empire, but later became one of the primary players for Indian independence. While the Indian National Congress may have been dominated by the Hindus, one of its central tenets was religious freedom for all religious groups on the subcontinent. Many Muslims, however, feared that when the Congress came into power in an independent India, it would not respect all religious minorities and take away property and rights from Muslims. The Muslim League was founded in 1906 to advocate a separate, Muslim-dominated country. These fractures within the independence movement can be seen in Hamidullah's political activities in the novel, where rifts between competing religious groups seem difficult to bridge except when it comes to their common enemy, the British (1.9.38).
However, by the time A Passage to India was published in 1924, a series of historical events encouraged the Congress and the Muslim League to work together for independence. These historical events provide a set of historical references for the events surrounding the trial in Forster's novel. In 1918, the Rowlatt Commission proposed what came to be known as the Rowlatt Acts, which took away key civil liberties away from Indians, including the admission of testimony from dead or absent witnesses (hence the outcry over Mrs. Moore's absence in the novel [2.24.85]). At this point, Gandhi, a member of the Indian National Congress and a founding figure in Indian history, organized non-violent demonstrations against the acts, including hartal, or work stoppages (thus the Sweepers' strike during Aziz's trial, which caused all the stoppages in the toilets [2.24.24]).
These demonstrations led to the infamous Amritsar Massacre of 1919 in circumstances quite similar to the novel. Peaceful Indian demonstrators had collected at Jallianwallah Bagh, but British and sepoy soldiers opened fire. Almost five hundred unarmed individuals were killed, and a thousand were wounded. During the so-called "riot," an Englishwoman was allegedly attacked by the Indians. She denied that she was attacked intentionally, cited the fact that she was helped by Indians after the attack, and refused any compensation. Despite her protestations, the general in charge instituted the notorious "crawling order," where Indians were forced to crawl along the road where the Englishwoman had been attacked (thus Mrs. Turton's comment that Indians should be forced to crawl (2.24.41). While there are no massacres in the novel, an attack on a white woman is also at the center of civil unrest, leading to the riots during the Moshurram festivities and after the trial.
Events such as the Amritsar massacre and the Rowlatt Acts further inspired Indians to seek independence, leading to an alliance between the Indian National Congress and the Muslim League during the Non-Cooperation Movement of 1920. But Forster's novel, in its depiction of the fissures within Indian society, shows how tenuous such an alliance was. In 1947, India did gain its independence, but also at the cost of partition with the establishment of Pakistan as a separate, Islamic state.
And by the way, if you happen to be in India, don't look for the Marabar Caves. The caves about which "nothing" can be said don't exist – they are, literally, nothing. Ironic, isn't it? The Marabar Caves are believed to be a composite of Malabar and the Barabar Hills, which are Buddhist caves north of Calcutta.