The IRA isn't defeated, but it knows that there is no chance of victory

When Mr Blair asks the IRA to disband he knows only too well that this is Gerry Adams' endgame as well

Writing after the death of Michael Collins at the hands of his former IRA comrades, Winston Churchill paid what Roy Jenkins has described as "realistic and unsentimental tribute". Churchill had been a member of the British team which helped negotiate the Anglo-Irish Treaty of 1920 and had come to develop respect for his erstwhile adversary. The feelings were mutual. I will quote the first half of Churchill's comments about Collins here, for they might well refer to a contemporary Republican leader now being asked to disband a secret army: "Successor to a sinister inheritance, reared among fierce conditions and moving through ferocious times ..."

The second half of Churchill's assessment of Collins I will come to later. Collins paid with his life because he turned against the diehards. Now Gerry Adams is being asked to make the final move that would end Ireland's long war. The demand for IRA disbandment made on Thursday by Tony Blair faces Adams with a choice not dissimilar to that which confronted Collins when he travelled to Britain to negotiate with Lloyd George and Churchill.

Like Collins, Adams enjoys majority support among the IRA leadership and his pro-peace position has been overwhelmingly endorsed by the electorate. The gains made by Sinn Fein north and south of the border have everything to do with abandoning the gun. For many nationalists the Good Friday Agreement took away the danger of moral contamination which support for Sinn Fein would previously have involved.

And like Collins, the Sinn Fein leader has accepted institutions and ideas which traditional republicans loathe. Sinn Fein has accepted a two-state solution, agreed to take part in partitionist parliaments and become part of the structure of British rule. These are all things Adams and Martin McGuinness said they would never accept. But just as Collins was forced by circumstance to accept partition, so Adams and the pragmatists have made their own hard choices.

There are significant differences, though. Collins was a leader of a young state and commanded a national army into which many of his IRA comrades could be absorbed. The new generation of Sinn Fein leaders have had to settle for far less: a couple of cabinet seats in the Stormont Assembly and the promise, not insignificant, that Britain has no selfish interest in remaining in Ireland. But there hasn't been a promise of a British withdrawal, much less the setting of a date.

When Collins took the terms offered by Lloyd George and Churchill he did so because war had ravaged his country, and he knew the IRA was on its last legs. He believed he no longer had the option of continuing with the armed struggle and turned towards pragmatic incrementalism.

In an immortal phrase, Collins said his movement had won "the freedom to achieve freedom". In different language Adams has been saying much the same thing to the IRA Army Council and to the Sinn Fein rank and file. The electoral success of Sinn Fein has helped his cause immensely, but so too has the relentless weakening of the IRA.

The organisation, which opted for ceasefire back in the mid-1990s, had been ravaged by informers and SAS ambushes. It wasn't defeated but it knew there was no chance of victory in the short or long term. By opting for a long-term ceasefire, the IRA leadership must have known that the army's destiny was being sealed. The punishment beatings and shootings, the intelligence gathering and the Colombia escapade are probably less the actions of a powerful force on the verge of a return to war, than those of a steadily weakening army trying to persuade its extremists that physical force still counts for something. The events of 11 September have also proved a critical part of the equation: the IRA will never again be able to raise gun money in the United States much less depend on the sympathy of Irish America.

The veteran IRA watcher Ed Moloney has just published an extraordinary account of the Provisional IRA's move towards constitutional politics. In The Secret History of The IRA he reveals the astonishing story of how Adams outmanoeuvred and marginalised the hardliners. Moloney has better sources in the IRA than any other journalist and when he describes Adams as a senior figure in the secret army, along with Martin McGuinness, one is inclined to pay attention. Mr Adams denies IRA membership, but Moloney provides information about Army Council meetings and Adams's contributions. One is left with the impression that when Adams says he will act as a link between the IRA and other parties in the political process he doesn't have too far to travel.

When Mr Blair asks the IRA to disband, he knows only too well that this is Adams's endgame too. The only difference is in the timing and the issue of verification. Adams wants the physical force movement to wither on the vine. Mr Blair has realised the fudge on which the process has survived is at an end. He needs something more tangible to offer the Unionists. Thus the piecemeal decommissioning of recent years will be inadequate, so too will any form of words which threatens to postpone the day of truth. If past form is anything to go by, the IRA will issue a statement soon denouncing the British Government's attitude. Don't pay too much attention to this. The considered version will come after prolonged consultations and it will be heavily influenced by the views of Adams and McGuinness. It will be big on the word "context". Context means what the British and loyalist paramilitaries will give in return.

There will be a demand for equal British and Unionist pressure on the loyalist paramilitaries. No republican leader will tell the IRA to disband while there remains the threat of attacks on nationalist areas from loyalists. Remember it was the catastrophic failure of the IRA to protect Catholic areas in 1969 which led to the birth of the Provisionals. Before considering disbanding, the IRA will want to know how the Government plans to protect Catholics in so-called "frontline" areas, but also a commitment to the so-called de-militarisation of Northern Ireland, in other words an end to any public military presence. The failure to disband will not mean a return to the scale of violence we witnessed for 30 terrible years. But the viciousness will bubble along, erupting from time to time and keeping everybody fearful.

The second part of Churchill's quote about Collins was as follows: "He supplied those qualities of action and personality without which the foundation of Irish nationhood would not have been established." Adams is a product of a violent past; he has defended the men of violence and, if Moloney's book is to be believed, he has directed actions of terrible cruelty. But only a man with his alleged record could have dragged the IRA away from war. Now more than ever the "qualities of action and personality" are needed.

The writer is a BBC Special Correspondent