Phase 1 — Before the Congress (1857–1885)

10 May 1857 — sepoys of the Bengal Army at Meerut mutinied, refusing to bite cartridges rumoured to be greased with cow and pig fat (an offence to both Hindu and Muslim soldiers), and marched on Delhi. What began as a military mutiny fast broadened into a widespread, if uncoordinated, rebellion across northern and central India — the Revolt of 1857, remembered variously as the "Sepoy Mutiny," the "Indian Mutiny," and, especially in Indian nationalist historiography (a framing popularised by V.D. Savarkar's 1909 book), the "First War of Independence."

The revolt's geography was patchy but its leadership was remarkable. At Delhi, the aged Mughal emperor Bahadur Shah Zafar was persuaded to lend his name as nominal head of the revolt, giving it a unifying symbolic centre even though he held no real command. At Kanpur, Nana Sahib (adopted heir of the last Peshwa, denied his pension by the Company) led the rising, with his lieutenant Tantia Tope conducting a skilled guerrilla campaign that outlasted most other centres of revolt. At Jhansi, Rani Lakshmibai, denied the right to adopt an heir under the Doctrine of Lapse, led her troops in person and died fighting near Gwalior in June 1858 — she remains the revolt's most celebrated figure, "the Joan of Arc of India" in colonial-era British accounts. At Lucknow, Begum Hazrat Mahal of Awadh directed resistance on behalf of her minor son after the annexation of Awadh in 1856 had inflamed local sentiment. In Bihar, the elderly Kunwar Singh of Jagdishpur led a determined campaign into his seventies.

The causes were layered: the immediate spark (greased cartridges) sat atop deeper grievances — the Doctrine of Lapse (Governor-General Dalhousie's policy of annexing princely states without a natural heir, used against Jhansi, Satara, and Nagpur among others), the annexation of Awadh, land revenue pressure on peasants, the displacement of traditional aristocracy and artisans, and missionary activity that stoked fears of forced conversion. The revolt was crushed by 1858, but its consequences were structural: the Government of India Act, 1858, ended East India Company rule outright, transferring administration directly to the British Crown; Queen Victoria's 1858 proclamation promised (with limited follow-through) non-interference in religion and equal treatment; and the Indian Army was reorganised to reduce the proportion of high-caste sepoys and increase reliance on so-called "martial races."

The following decades saw limited constitutional tinkering and the first stirrings of organised, educated-Indian political activity:

• 1861 — the Indian Councils Act enlarged legislative councils marginally and permitted (still very limited) Indian participation; the same year the Indian High Courts Act established High Courts at Calcutta, Bombay and Madras.
• 1876 — Surendranath Banerjee founded the Indian Association in Calcutta, campaigning notably against the age limit for the Indian Civil Service examination, which discriminated against Indian candidates.
• 1878 — the repressive Vernacular Press Act, gagging Indian-language newspapers, was passed under Lytton and repealed only in 1882 under the more liberal Viceroy Lord Ripon (who also gave India the Ripon local self-government reforms of 1882, seeding municipal and district boards).
• 1883–84 — the Ilbert Bill controversy: a bill permitting Indian judges to try European offenders provoked a furious, openly racist European backlash in Calcutta that forced the government to dilute the bill. The episode radicalised educated Indian opinion — if merit and loyalty still could not earn equal treatment under law, many concluded, only organised political pressure would. It is widely seen as the immediate trigger that made the founding of an all-India political body, a year later, feel necessary.