They came on Saturday to Dublin in their tens of thousands, old and young, from every corner of the island, black and white, Christians and Muslims, and reflecting shades of politics that reached well beyond the "usual suspects" into the ranks of middle Ireland.
Up to 100,000, with more in Belfast, insisted that a war against Iraq will not be fought in their name and that complicity at Shannon with a military build-up must be ended.
The weekend's synchronised demonstrations in 600 cities on every continent included up to one million marching in London, three million in Spain, and hundreds of thousands in Rome, Berlin, Paris, New York and Sydney. It marked, in spectacular fashion, the coming of age of globalised protest as an alternative force.
The extraordinary Dublin turnout should make the Taoiseach, heading today to the special EU Brussels summit on the crisis, pause for thought. It was the genuine outpouring of an internationalist spirit which many feared had been lost.
The Irish Times/MRBI poll published on Saturday found that 68 per cent of Irish voters would oppose unilateral action by the US, and yet this newspaper reported last week that senior ministers believe the State has no alternative but to back the US in whatever campaign it decides to wage.
Yet, as Mary Robinson argued in these pages in relation to the international moral legitimacy of a last-course resort to war, it must reflect "the combined will of the world's governments and their people." In other words, more is needed than a majority of the Security Council or even the nations of the world - a consensus of world opinion is required.
Such a consensus test should also be met domestically if the Government wishes to implicate this State in support for a unilateralist invasion of Iraq. Saturday's march and poll made clear there can be no such consensus, and the Government must take note.
What sense, moreover, would be made of Mr Brian Cowen's repeated, correct insistence on the unique status of the UN as a legitimiser of military force, if the Government was to develop an a la carte attitude to the UN by blindly following the US?
Indeed, speakers at Saturday's rally reflected, more or less obliquely, a real dilemma that many in Ireland will face if the Security Council does eventually endorse US action.
Some, like Mr Joe Higgins and Mr Richard Boyd Barrett, already dismiss the UN as an irrelevant forum, inadvertently in so doing mimicking the hard right in the US. Others, like Mr David Begg of the ICTU, spoke more carefully of the dangers of unilateralism, acknowledging that war can, in certain cases, be justified. But not on this occasion.
The Government, weighing the value of the US relationship, ignores such mainstream critics and defenders of the UN's credibility at its peril.