The UN resolution supporting an Arab League peace plan was the most determined effort so far by the Security Council to try and respond to the crisis in Syria.
It now lies in tatters after the double veto by Russia and China.
The scale of the defeat was registered in the gloom on the faces of Western and Arab envoys, and in the bitter exchanges in the council after the vote.
Using words like "disgusted" and "appalled", Western diplomats accused Russia and China of holding the council hostage, and of complicity in the policy of repression carried out by the regime of President Bashar al-Assad.
The disappointment was all the deeper because this was the second double veto on Syria, and because this time agreement had seemed possible.
The resolution had the support of the 13 other council members and of the group representing the region - the Arab League.
In intense negotiations diplomats seem to have met many of the Russian objections: they took out reference to anything that might have suggested support for sanctions or an arms embargo, and added assurances that the resolution could not be used to authorise military intervention or regime change.
They removed explicit reference to the elements of the Arab peace plan - particularly a timetable spelling out a process for Mr Assad to hand powers to a deputy who would oversee preparations for new elections. Although they insisted that support for the plan itself was a red line.
Despite all of this the Russians vetoed.
In broad terms, their decision was coloured by the strategic and commercial interests they have invested in a decades-long alliance with the Assad regime, and by their policy of non-intervention in the affairs of a sovereign state.
But there were two other reasons why they refused to accept this specific resolution.
First of all, they were never happy with the way it came about.
They supported the Arab League observer mission despatched to Syria in December, but they didn't think its conclusions warranted the subsequent league decision to promote a political process that in essence saw Mr Assad step aside.
Rather, the Russians suspected that the observer mission had been hijacked by Qatar and Saudi Arabia (countries hostile to Syria) backed by Western powers, and that their proposal was a thinly disguised attempt at regime change.
Because the Russians thought that was the real intention, it was always going to be very difficult to get their full support for the Arab plan, especially as the Syrian government had rejected it.
Even in the last amendments they put forward, they were trying to weaken its elements, "taking account" of the timetable for political transition, rather than adhering to it.
Secondly, the Russians highlight the element of armed conflict in the violence, rather than simply focusing on government repression of civilians.
They say the Security Council should also be making demands of the armed opposition, not just the regime, or it will be taking sides in a civil war.
Again, their last minute amendments reflected this view, declaring, for example, that any military withdrawal from cities and towns be done in conjunction with an end to rebel attacks.
This was just too much of a concession for the West to accept, especially on a day when government forces had been relentlessly shelling the city of Homs.
So what happens next?
The British ambassador to the UN, Mark Lyall Grant, has promised to bring the Arab League plan back to the council if the bloodshed continues, although there is little to suggest the Russians would not again reject it for all the reasons they have cited.
More likely is that diplomatic efforts will run along different and possibly opposing tracks.
Western nations have said they will continue strong support for the Arab peace plan, working with the Arab League to pressure and isolate the Assad regime.
Russia has also announced its own separate initiative. On Tuesday Foreign Minister Sergei Lavrov and the head of Russia's foreign intelligence service will go to Damascus. People will be waiting to see whether the Russians can succeed where the world has failed - in getting Mr Assad to sign on to a political transition plan that would end the conflict.