Wars are won when the people, government and army work together for a common cause in which they genuinely believe. Whereas the people may be initially uncertain about military intervention, politicians will often be the strongest advocates - blinded by the imperatives of their political views. It will invariably be military commanders who are most cautious about using force - for they understand better than most the consequences of engaging in war.

Although in a true democracy they must remain subordinate to their political masters, they have a clear responsibility to point out when political strategies are flawed or inadequately resourced. Since they might also have to ask their soldiers to sacrifice their lives, they must be assured that a war is just, legal and the last resort available. Yet three years ago this country was somehow led by the prime minister into war in Iraq where few, if any, of these requirements were met.

Most importantly a clear justification for the war in Iraq was never sufficiently made by Tony Blair - for the intelligence he presented was always embarrassingly patchy and inconsistent. What is more, his unequivocal statement to the House of Commons that Saddam Hussein possessed weapons of mass destruction that could be used within 45 minutes was made without being properly validated - for it was decided in Washington and London to launch the invasion of Iraq early, on the basis of the flimsy evidence available. This was done without asking the UN weapons inspectors, who were actually on the ground in Iraq, to investigate this allegation. Ultimately, as the inspectors suspected and as we now all know, it turned out that there were no such weapons. Britain had been led into war on false pretences. It was a war that was to unleash untold suffering on the Iraqi people and cause grave damage to the west's prospects in the wider war against global terror.

Nevertheless, today the prime minister seeks to persuade the world that the war was justifiable because Saddam Hussein was toppled and there now exists in Iraq a slender hope of democracy. The Iraqi elections are a creditable achievement by the coalition forces. But it must be remembered that a general election was previously held in Iraq in 1956, and within two years the country had fallen under military rule. Without adequate security and the necessary democratic institutions in place, there are absolutely no long-term guarantees that democracy will endure.

Before the invasion, regime change was never cited as a reason for going to war. Indeed, Mr Blair insisted that regime change was not, nor ever could be, a reason for going to war. Had such a justification been fully debated in parliament, it is exceedingly unlikely that the necessary political support would have been forthcoming. It was the apparent need to defend ourselves against a dire threat - so vividly described by Mr Blair in the Commons - that finally won the political argument.

During the build-up to war and since, most of the electorate of this country have consistently opposed the decision to invade. People have seen their political wishes ignored for reasons now proved false. But there has been no attempt in parliament to call Mr Blair personally to account for what has transpired to be a blunder of enormous strategic significance. It should come as no surprise therefore that so many of this country's voters have turned their backs on a democratic system they feel has so little credibility and is so unresponsive.

One obvious way of re-engaging these disaffected voters would be for parliament to accept that it wrongly supported the war - but only because it believed what Mr Blair told them. Now it is clear that parliament was misled by Mr Blair, either wittingly or unwittingly, parliament should also call on him for a full explanation as to why he went to war. It is not a sufficient excuse for Mr Blair to say that he acted in good faith and that his decisions were based on the intelligence he had been given. For it is the clear responsibility of people in his position to test intelligence. No intelligence can ever be taken at face value. Indeed it is negligent so to do.

Parliament should therefore ascertain how far the prime minister did evaluate intelligence regarding WMD and how he assessed the reliability of the many sources that provided that intelligence. It should ask him what corroborating evidence there was for his specific statement about WMD - and why more use was not made of the UN inspectors on the ground in Iraq to test the validity of that statement. It should inquire just how much he discounted the mass of intelligence that came in from the Iraqi National Congress - a body that had a vested interest in removing Saddam from power. The list of possible questions is huge and would no doubt be usefully expanded during any hearings.

Mr Blair is an able barrister who should relish the opportunity to put his side of the case. No one can undo the decision to go to war. But the impeachment of Mr Blair is now something I believe must happen if we are to rekindle interest in the democratic process.

General Sir Michael Rose was adjutant general of the British army and commander of the UN protection force in Bosnia. Email comments to: comment@guardian.co.uk  

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