He joined the ANC in 1940. In 1943, together with Nelson Mandela and Oliver Tambo, he joined the ANC Youth League, founded by Anton Lembede, of which he was initially the treasurer. He later distanced himself from Lembede after Lembede (died 1947) had ridiculed his parentage (Sisulu was the son of a white foreman). Sisulu was a brilliant political networker and had a prominent planning role in the militant Umkhonto we Sizwe ("Spear of the Nation"). He was made secretary general of the ANC in 1949, displacing the more passive older leadership, and held that post until 1954. He also joined the South African Communist Party.
As a planner of the Defiance Campaign from 1952, he was arrested that year and given a suspended sentence. In 1953, he travelled to Europe, the USSR, Israel, and China as an ANC representative. He was jailed seven times in the next ten years, including five months in 1960, and was held under house arrest in 1962. At the Treason Trial (1956–1961), he was eventually sentenced to six years, but was released on bail pending his appeal. He went underground in 1963, resulting in his wife being the first woman arrested under the General Laws Amendment Act of 1963 (or "90-day clause". He was caught at Rivonia on 11 July, along with 16 others. At the conclusion of the Rivonia Trial (1963–1964), he was sentenced to life imprisonment on 12 June 1964. With other senior ANC figures, he served the majority of his sentence on Robben Island.
Release from prison
In October 1989, he was released after 26 years in prison, and in July 1991 was elected ANC deputy president at the ANC's first national conference after its unbanning the year before. He remained in the position until after South Africa's first democratic election in 1994
Sisulu, along with Lembede, Mandela, Oliver Tambo, and Ashley Mda, was elected to the executive committee of the newly established ANC Youth League in 1944. Albertina Sisulu was the only woman amongst approximately 200 men present at the founding conference of the League’s Transvaal branches. While the Youth League in its early stages, it was heavily influenced by Anton Lembede’s militant African nationalism, Sisulu always took a more pragmatic line, especially around the ANC collaboration with the Communist Party and the Indian Congresses.
During the Second World War, Sisulu campaigned against Black South Africans joining the army. He supported the Youth League in pressing for the reform of the ANC and for the ANC to adopt boycotts and other forms of direct action to address the needs of the disenfranchised. During this period he had his first clash with the police when he was charged after a scuffle on a train with a white ticket collector who had confiscated an African child's season ticket.
During the 1946 African Mineworkers' Strike, which was opposed by the ANC, Sisulu was approached and agreed to sabotage the railway line between Soweto and New Canada station. However, the person who had promised to provide him with the bomb did not arrive and this early use of sabotage as a tactic of resistance failed.
Sisulu rose very rapidly in the ranks of the ANC and became a member of the Transvaal executive in addition to being secretary of the Youth League. At the ANC national conference in December 1949, Sisulu was instrumental in the ANC’s adoption of the Youth League's militant Program of Action. At the same conference he was elected ANC Secretary-General, narrowly defeating Dan Tloome, the candidate of the ANC's left wing. Sisulu’s fearless, totally dedicated and formidable strategic and organisational abilities are recognised today as being the main factor in transforming the ANC into a mass-based militant national organisation.
In 1950, the government of DF Malan prepared to implement its new apartheid policy by introducing a series of harsh racial laws and proposing to ban the Communist Party. The ANC took the first steps to oppose the government by forming a committee to coordinate joint campaigns with the Indian Congress and the largely coloured Cape Franchise Action Committee. This was the beginning of what came to be known was the Congress Alliance.
Walter Sisulu and Yusuf Cachalia were appointed joint secretaries and their first move was to call for a national work stoppage on 26 June 1950 to protests against the new repressive apartheid laws. James Moroka, ANC president at the time, lived in the Orange Free State and was isolated from the day-to-day running of the organisation in the Transvaal and the industrial and commercial heart of South Africa (Johannesburg). Consequently, Sisulu took over many of Moroka's responsibilities in addition to being Secretary-General. As leader of the ANC, Sisulu played a central role in the advocating and the planning the 1952 Defiance Campaign. He led a group of passive resisters and was arrested and imprisoned for a brief period before being served with the first of his many banning orders under the Suppression of Communism Act. In December 1952, Sisulu, Mandela, Moroka and others were tried under the Suppression of Communism Act for their leadership role in the Defiance Campaign. All 20 accused were sentenced to nine months' imprisonment with hard labour, suspended for two years.
Sisulu was re-elected as ANC Secretary-General in the same month, and in 1953 spent five months touring China, the Soviet Union, Israel, Romania and the United Kingdom. The tour to the socialist countries convinced Sisulu to join the outlawed and newly reconstituted the South African Communist Party on his return. His membership of the underground communists is again recognised as one of the most important factors cementing the relationship between the ANC and SACP.
Walter and Mandela were banned for six months and barred from attending any gatherings or addressing meetings. He secretly continued his ANC work, and was part of the organising committee that met in secret to organise the Freedom Charter campaign and The Congress of the People in 1956. In December Sisulu was among the 156 people arrested for High Treason. The preparatory examination of the Treason Trial began on 19 December in the Johannesburg Drill Hall. Sisulu remained a defendant in the subsequent hearings, which ended on the 29 March 1961 when he, and the remaining 30 accused, were finally acquitted.
In April 1982 Walter Sisulu was admitted to Groote Schuur hospital in Cape Town for a ‘routine medical examination’. In the same month Sisulu, Mandela, Raymond Mhlaba, Andrew Mlangeni and Wilton Mkwayi were moved from Robben Island to Pollsmoor prison in Cape Town. Later they were joined by Ahmed Kathrada. The reason for the move was so that the Botha government could ensure greater secrecy in their effort to convince Mandela to accept their conditions for a negotiated settlement with the ANC. Mandela turned to his fellow prisoners, and Sisulu in particular, for advice in his dealings with the government intermediaries. One of the conditions that Mandela insisted on was the early release of his co-accused and on 15 October 1989, after 26 years in prison, Rivonia trialist’s Walter Sisulu, Ahmed Kathrada, Andrew Mlangeni, Elias Motsoaledi, Raymond Mhlaba and Wilton Mkwayi, were released along with Oscar Mpetha, the veteran ANC and SACP Cape Leader, and Japhta Masemola, a Pan Africanist Congress (PAC) leader. Their release was greeted with scenes of wild celebration around the country. Soweto was awash with black, green and gold and a huge ANC flag was draped across the walls of the Sisulu house. Though still banned, the ANC had come out into the open.Less than three months later, on 2 February 1990, the ANC was unbanned and Nelson Mandela was released 9 days later.
Sisulu subsequently met with the external wing of the ANC in Lusaka and was asked to lead the ANC inside South Africa. This involved re-establishing ANC structures within the country and preparing for a national conference to be held inside South Africa on 16 December 1990. Sisulu formed part of the ANC delegation that met with representatives of the government at Groote Schuur, Cape Town, in May 1990. He was elected in 1991 as Deputy President of the ANC at the ANC’s first conference held inside the country since its banning more than three decades earlier.
In April 1994 South Africans enjoyed their first ever free and fair elections and overwhelmingly elected the ANC to government. With millions of their comrades, Walter and Albertina Sisulu celebrated the convincing electoral victory of the organisation to which they had devoted most of their lives. Six weeks later, they celebrated their 50th wedding anniversary on I7 July 1994. Over one thousand people celebrated with them at the Vista University Hall in Soweto and the occasion was a fitting tribute to two of South Africa's most celebrated leaders.
Walter Sisulu was deputy president of the ANC until ill health forced him to retire from active politics in 1994. He continued to be passionately committed to the wellbeing of his community, especially children and young people and he and Albertina devoted much of their time to the Albertina Sisulu Foundation which built a multi-purpose community centre in Orlando West, Soweto. The Sisulu’s lived in a house in Soweto for most of their lives. They moved to a new house in Linden in Johannesburg only four years before Walter's death. Walter Ulyate Max Sisulu died on 5 of May 2003, a few days before his 91st birthday.