Mr Kasrils was Film script writer in Johannesburg from 1958 to 1960; a TV and film director for Lever Brothers advertising division in Durban from 1960 until 1962.
He joined the African National Congress (ANC) in 1960.
and was also Secretary of ANC-aligned Congress of Democrats in Natal in 1961. He was founder member of Umkhonto we Sizwe (MK) as member of Natal Regional Command in 1961 and Commander of Natal Regional Command in 1963.
He completed a general military course and specialist course in military engineering in Odessa in 1963 and served ANC for 27 years, based in London, Luanda, Maputo, Swaziland, Botswana and Lusaka. He was member of Umkhonto we Sizwe (MK)'s High Command; Chief of MK Intelligence after completing specialist course to the rank of Brigadier in former USSR in 1983.
He served on ANC's Politico-Military Council from 1985 until 1989; worked underground for the ANC in South Africa on Operation Vula between 1990 and 1991; and he headed the ANC's Campaign Section from 1991 to 1994. He also became member of the Transitional Executive Council's (TEC) Sub-Council on Defence in 1994.