Military personnel and their associates 'have been involved, and in some cases are still involved, in illegal and or unauthorised activities and malpractices', the President said. 'There are indications that some of the activities and some of the individuals might have been motivated by a wish to prevent us from succeeding in our goals.'
In confirming that there was a conspiracy inside the South African Defence Force to destabilise black politics, Mr De Klerk was not telling his countrymen something they did not already know. So much evidence has emerged in the past two years that it had become almost impossible for anyone but the government to deny it. But the President's press conference yesterday will have left one question on everybody's lips: how much did he know?
His line is that elements of the security forces were out of control, ministers were not told what was going on, and that the buck stops with the generals - six of whom are to pay with their jobs. They are at the very least to blame for failing to stop it, and may indeed have been deeply involved, in which case they will be tried.
But the evidence has long been so overwhelming that it is difficult to avoid the conclusion that he could have escaped knowing about it only by deliberately averting his gaze.
The charge against the security forces, and in particular against Military Intelligence (MI), is that they stoked and manipulated the township violence that has cost a minimum of 5,000 lives. There are lesser charges: of assassination, intimidation, smear tactics, disinformation and general espionage, all directed against the ANC and its offshoots.
None of these has Mr De Klerk specifically admitted. Under great pressure at yesterday's press conference, he would say only that SADF members and agents had indulged in illegal acts that probably led to deaths.
But the floodgates are open. The 'third force' is acknowledged, if only implicitly, and prosecutions are almost certain to tell us more.
The idea of a 'third force' grew out of the manifest bias shown by the security forces in the long-running conflict between African National Congress and Inkatha supporters in Natal. When the violence spilled over into the townships around Johannesburg in 1990, the same bias was apparent, and the first suspicions were voiced that the killing was being orchestrated.
The first hard evidence of this, did not, however, emerge until June last year, when a former MI officer, Nico Basson, told the Independent that MI was arming Inkatha and deploying agents to stir up violence.
The following month, a more direct link was revealed when Felix Ndimane, a former sergeant in an army Special Forces regiment, said he had taken part in massacres on commuter trains and other attacks on black civilians. His unit was under MI command.
Mr De Klerk appointed a general to investigate, there was a whitewash and the 'mischief- making press' was condemned. In January, Mbongeni Khumalo, a former member of Inkatha's central committee, revealed that he and other senior Inkatha members had received training from MI. Then in May, a climax was reached when the New Nation newspaper alleged that the chief of Military Intelligence, General Christoffel van der Westhuizen, had authorised four political assassinations in 1985.
While these stories made headlines, supporting evidence was tumbling out of South African courtrooms. It was, by the middle of this year, to paint a detailed picture of MI thinking, operations, tactics and structures, all designed to undermine the process of reform and damage the ANC. Bloodshed on an appalling scale was involved.
This, however, was not enough to shake the government's public faith in the probity of its soldiers. The odd bad apple was up to no good, ministers admitted grudgingly, but that was all.
The chain of events which finally forced a 'shocked' Mr De Klerk to make his confession yesterday, began with a former policeman named Ferdi Barnard. A convicted murderer who had spent four years in jail, Barnard worked for several years for the Civil Co-operation Bureau, a violent clandestine organisation run by MI. Last month he was accused in court of murdering an ANC activist, David Webster, in 1989.
Last year, Mr Barnard set up and directed an operation to infiltrate, subvert and discredit the ANC's military wing, Umkhonto we Sizwe. It had ready access to government data, from criminal files to tax records, and to private sources such as credit bureaus. It enlisted bugging experts, prostitutes and night-club managers.
This first came to light in court, when a man charged with possession of a machine-gun explained that he had been given it by Barnard, who worked for MI. Further details of Barnard's activities were unearthed and published by the Afrikaans newspaper, Beeld.
Lurid as it is, however, this tale of a murderer leading a security forces dirty tricks operation was just one of many such tales. What made it different was that it was taken up by Richard Goldstone, the Appeal Court judge appointed last year by Mr De Klerk to chair an inquiry into political violence. Justice Goldstone, who is known for his scrupulous impartiality and fearlessness, set his investigators to uncover the full truth about Barnard. Documents were seized from an MI operations centre, and the resulting 13- page report landed on Mr De Klerk's desk last month like a fizzing stick of dynamite.
Not only did it confirm the worst about Ferdi Barnard's operations, it also showed that he had been recruited by General 'Witkop' Badenhorst, a former chief of MI. Worse, Judge Goldstone went out of his way to show that the Minister of Defence at the time of the Beeld revelations, Roelf Meyer, who is still in the government, had issued a 'false' denial of the story. There had been a cover-up.
The President appointed an air force general, Pierre Steyn, to carry out an inquiry into MI activities, and the first result was seen yesterday: two full generals, four brigadier-generals and 10 other security force members sacked, and seven more suspended pending further investigations. It is a massacre among the top brass. It is also a vindication of the work of Judge Goldstone and his team of lawyers and journalists who have chronicled the manifestations of the 'third force'; and, above all, of the whistle-blowers - defectors, witnesses and exiles - who risked their lives to provide the evidence.
Proof of the risks they ran was vividly demonstrated in recent weeks during the inquest into the death of Bheki Mlangeni, a lawyer killed by a parcel bomb last year. The bomb was intended for Dirk Coetzee, a former South African policeman who defected to the ANC with stories of political death squads. Papers produced during the inquest showed that an MI team pursued Mr Coetzee to London and used contacts in the Royal Ulster Constabulary to set up another hit.
How far the 'third force' might go to protect minority rule came out in evidence from a former MI colonel, Gert Hugo. 'Under lock and key at every group headquarters is an operational contingency plan,' he said. 'It's a contingency plan for a coup.'
Col Hugo said that at the time of Nelson Mandela's release, a top-secret signal from Pretoria warned of the threat of anarchy and revolution. 'The hidden message, but it was absolutely clear, was that we had to make contingency plans for a total military take-over when this happened.'