Adams has often said that he has never been a member of the Provisional Irish Republican Army (IRA). However, several writers and journalists such as Ed Moloney, Richard English, Peter Taylor and Mark Urban have all said Adams was part of the IRA leadership during the 1970s. Adams has called Moloney's claims "libellous."
In 1978, Gerry Adams became joint-vice-president of Sinn Féin and he led a challenge to the Sinn Féin leadership of President Ruairí Ó Brádaigh and joint-Vice President Dáithí Ó Conaill. Others who supported Adams and were from Belfast included Jim Gibney, Tom Hartley, and Danny Morrison. Some say Ruairí Ó Brádaigh was a more traditional Irish nationalist and that the northern leadership which surrounded Adams wanted to act faster and in different ways if they had to.
The 1975 IRA-British truce is often viewed as the event that began the challenge to the original Provisional Sinn Féin leadership, which was said to be Southern-based and dominated by southerners like Ó Brádaigh and Ó Conaill. However, the Chief of Staff of the IRA at the time, Seamus Twomey, was a senior figure from Belfast. Others in the leadership also lived in the North, including Billy McKee from Belfast. Adams was supposed to have become the most senior figure in the IRA Northern Command because he wanted only military action, but during his time in prison, Adams came to thought about his ideas and became more political.
It is alleged that "provisional" republicanism was founded on its opposition to the communist-inspired "broad front" politics of the Cathal Goulding-led Official IRA, but this too is disputed.
Some of the main reasons that the Provisional IRA was founded in December 1969 and provisional Sinn Féin was founded in January 1970, was that people like Ó Brádaigh, O'Connell, and Billy McKee wanted new political bodies and did not want to work in or with the existing bodies such as the Parliament in London. Another was the failure of the Goulding leadership to defend nationalist areas against attacks by Loyalists and sometimes even the police. At the December 1969 IRA convention and the January 1970 Sinn Féin Ard Fheis (the Irish words for a party conference or convention) the delegates voted to participate in the Dublin (Leinster House), Belfast (Stormont) and London (Westminster) parliaments, the organizations split into Provisional and Official parts. Gerry Adams, who had joined the Republican Movement in the early 1960s, did not go with the Provisionals until later in 1970.
Republicans like Ruairí Ó Brádaigh said that the only legitimate country in Ireland was the Irish Republic declared in 1916. They said the legal government was the IRA Army Council because the last remaining anti-Anglo-Irish Treaty deputies of the Second Dáil made them the government. (Adams agreed to this idea of republican political legitimacy until quite recently - however in his 2005 speech to the Sinn Féin Ard Fheis he rejected it.)
When Sinn Féin any won seats in the British or Irish parliaments they never went to the parliaments. At its 1986 Ard Fheis, Sinn Féin changed its and constitution to allow its members to sit in the Dublin parliament (Leinster House/Dáil Éireann). This made Ruairí Ó Brádaigh lead a small walkout, just as he had done years earlier to create Provisional Sinn Féin. This minority which still believed in abstentionism, called themselves Republican Sinn Féin (or Sinn Féin Poblachtach in Irish), and says that they are the true Sinn Féin.
Adams' leadership of Sinn Féin was supported by a Northern-based group that included Danny Morrison and Martin McGuinness. Adams and others, over time, pointed to Sinn Féin election wins in the early and mid-1980s, when hunger strikers Bobby Sands and Kieran Doherty were elected to the British House of Commons and Dáil Éireann, and they pushed to get Sinn Féin to become more political and less paramilitary. This policy was a success and Adams and McGuinness, and others were elected to the House of Commons, but never attend. Sinn Féin still abstains from Westminster.
At this time most ordinary people in Britain knew about Adams because they could not hear him. Prime Minister Margaret Thatcher banned radio and television stations from broadcasting his voice. All Irish republican organizations and loyalist terrorist organizations were banned like this, but Adams was the only person important enough to appear regularly on TV. This ban was imposed after the BBC interviewed Martin McGuinness. and the British Government thought that some groups were getting too much publicity.
A similar ban, known as Section 31, had been the law in the Republic of Ireland since the 1970s. However, media outlets soon found ways around the ban, first by the use of subtitles, and later and more commonly by using actors to read his words over the pictures of him speaking.
This ban was made fun of in cartoons and satirical TV shows, notably "Spitting Image", and in "The Day Today". It was also criticized by freedom of speech organizations worldwide and British media personalities, including BBC Director-General John Birt and BBC foreign editor John Simpson. The ban was lifted by Prime Minister John Major on 17 September 1994.
Sinn Féin continued its policy of refusing to sit in the Westminster parliament even after Adams won the Belfast West constituency. He lost his seat to Joe Hendron of the Social Democratic and Labour Party (SDLP) in the 1992 general election. However, he easily regained it at the next election in May 1997.
Under Adams, Sinn Féin moved away from being a political voice of the Provisional IRA to becoming a professionally organized political party in both Northern Ireland and the Republic of Ireland.
SDLP leader John Hume MP realized that a negotiated settlement might be possible and began secret talks with Adams in 1988. These discussions led to unofficial contacts with the British Northern Ireland Office under the Secretary of State for Northern Ireland, Peter Brooke, and with the government of the Republic under Charles Haughey – although both governments maintained in public that they would not negotiate with "terrorists".
These talks provided the basis for what was later to be the Belfast Agreement, as well as the Downing Street Declaration and the Joint Framework Document.
These negotiations led to the IRA ceasefire in August 1994. The new Irish Taoiseach (prime minister) Albert Reynolds had played a key role in the Hume/Adams talks through his Special Advisor Martin Mansergh, thought the ceasefire as permanent. However, the IRA ended its ceasefire because of the slow pace of developments, partly because British prime minister John Major needed the votes of the Ulster Unionist Party in the House of Commons.
Later there was a new ceasefire, and there were talks between teams from the British and Irish governments, the Ulster Unionist Party, the SDLP, Sinn Féin and representatives of loyalist paramilitary organizations, under the chairmanship of former United States Senator Mitchell. The talks produced the Belfast Agreement (also called the "Good Friday Agreement" as it was signed on Good Friday, 1998). Under the agreement, structures were created to show that some people on the island of Ireland were Irish and others wanted to be British. A British-Irish Council and the Northern Ireland Assembly were set up.
Articles 2 and 3 of the Republic's constitution, "Bunreacht na hÉireann", which claimed sovereignty over all of Ireland, were reworded, and a power-sharing Executive Committee was provided for. As part of their deal Sinn Féin agreed to abandon its abstentionist policy regarding a "six-county parliament", and took its seats in the new Assembly based at Stormont Sinn Féin ran the and running the health and social services and the education ministries in the power-sharing government.