(Detailed year-by-year coverage is in the dedicated "Freedom Movement" and "Congress Sessions" notes files — this section gives the broad framework.)

Early associations: Pre-Congress bodies included the Land Holders' Society (1838), British India Association (1851), East India Association (1866, founded by Dadabhai Naoroji in London), Poona Sarvajanik Sabha (1870, M.G. Ranade), and the Indian Association (1876, Surendranath Banerjee and Anandamohan Bose).
Indian National Congress (INC) founded in 1885 by Allan Octavian Hume (a retired British civil servant), with W.C. Bonnerjee as the first president, at Bombay — historians debate the "safety valve theory" (that the British encouraged its founding to channel discontent safely) versus the view that it emerged from genuine indigenous political awakening.
Moderate phase (1885–1905): Leaders like Dadabhai Naoroji, Gopal Krishna Gokhale, Pherozeshah Mehta, and Surendranath Banerjee favoured constitutional methods — petitions, resolutions, and dialogue — seeking greater Indian representation and economic reform within the British constitutional framework.
Partition of Bengal (1905): Ordered by Viceroy Lord Curzon, ostensibly for administrative convenience but widely seen as a "divide and rule" strategy to weaken Bengali nationalism along communal lines. This triggered the Swadeshi Movement — boycott of British goods, promotion of indigenous industries, and a marked radicalisation of the nationalist movement. The partition was eventually annulled in 1911.
Extremist phase (1905–1918): Leaders known as the "Lal-Bal-Pal" trio — Lala Lajpat Rai (Punjab), Bal Gangadhar Tilak (Maharashtra, who declared "Swaraj is my birthright and I shall have it"), and Bipin Chandra Pal (Bengal) — advocated more assertive methods including boycott and passive resistance.
Surat Split (1907): The Congress split into Moderate and Extremist factions at the Surat session, reuniting only at the Lucknow Session (1916), which also saw the historic Lucknow Pact between the Congress and the Muslim League (founded 1906 at Dhaka), agreeing on a joint scheme of constitutional reforms including separate electorates for Muslims.
Home Rule Movement (1916): Led separately by Bal Gangadhar Tilak and Annie Besant, inspired by the Irish Home Rule movement, demanding self-government within the British Empire.