Well known for being sentenced, along with Nelson Mandela, Govan Mbeki, Walter Sisulu and others in the Rivonia Trial, he was an active member of the ANC and the South African Communist Party (SACP) all his adult life.
Mhlaba was the first to be arrested for disobeying apartheid laws during the nationwide Defiance Campaign of 1952 together with Govan Mbeki and Vuyisile Mini for three months in Rooi Hel ('Red Hell' or North End Prison, Port Elizabeth).
The campaign was launched in Port Elizabeth when Mhlaba led a group of volunteers singing freedom songs through the "Whites Only" entrance of the New Brighton Railway Station.
[citation needed] After the ANC was banned on 8 April under the Unlawful Organisations Act, the party took up the armed struggle forming its military wing Umkhonto we Sizwe.
[citation needed] On 11 July 1963 the South African apartheid government raided the ANC's underground headquarters in Rivonia, north of Johannesburg.
Mhlaba and 10 other ANC and SACP leaders including Ahmed Kathrada, Walter Sisulu and Govan Mbeki were arrested and Nelson Mandela was already in prison.
The committee educated and supported younger imprisoned members, formulated policies on day-to-day concerns, prisoners' complaints, and strikes, and enforced discipline within their isolation unit.
"[1] After his release from prison on 15 October 1989, he was elected to the ANC national executive and the South African Communist Party central committee.
He was chairperson of a black economic empowerment consortium involved in the Coega port project, but suffered a stroke on 19 July 2003, recovering quickly.