Bhattarai had participated in a long struggle to modernize the Nepalese political system, aiming to transform a society that was isolated for centuries from the outside world. He started politics to end the 104-year-rule of the
Rana Dynasty. During the political movement of 1950 to overthrow the Rana autocracy, initiated by the Bairgania Conference of the
Nepali Congress on 26–27 September 1950 (Ashvin 10–11, 2007 BS), he was in charge of armed group
Congress Mukti Sena fighting in
Gorkha district. This armed struggle was initiated by the Nepali Congress, of which he was founding member. The armed revolution by the Nepali Congress was supported by
King Tribhuvan, who was in exile, and by
Indian and
Burmese socialists. The armed revolution ultimately brought an end to the 104-year-rule of the Rana Dynasty on 18 February 1951 (Falgun 7, 2007 BS). This day is celebrated as
Democracy Day and is a public holiday in Nepal. After the first parliamentary election of 1959, at the age of 36, he became Speaker of lower house of parliament, though he was not an elected member. After the coup of 1960, Bhattarai was held without trial for eight years at the
Sundarijal Military Detention Camp. Bhattarai was nominated as the officiating President of the Nepali Congress on 12 February 1976 (Falgun 1, 2025 BS) by then party President
B. P. Koirala. He held this post for over 20 years, during which time he was a key figure in Nepal's democratic movement. He was elected President of the Nepali Congress by the Eighth National Conference of the Nepali Congress, held in January 1992 (Falgun 2049 B S). ==Prime Minister of Nepal==