Then, to Cameron's apparent fury, Miliband declined to support it anyway, thus setting the stage for an extraordinary event: the first defeat by a government on a matter of national defence in over 230 years.
I do not, in all honesty, that Miliband was at all confident he would defeat the government. I believe he thought he was acting in good faith to ensure that all the i's were dotted and t's crossed before British troops were sent into action. But that is what happened.
Afterwards Cameron, apparently to the surprise of the Miliband entourage, removed the possibility of intervention from the table.
Miliband, given a way out of his predicament of being seen to have torpedoed the process, took it and said he was not really interested in intervention, either. Tellingly, he said:
Military intervention is now off the agenda for Britain. There would have been nothing worse than intervention without full international support.Presumably this meant Russia and China in the UN Security Council, because it is clear that US and France are proceeding to some kind of action (interestingly, it was earlier confirmed to me that this was not the case, that he would not be beholden to Russian and Chinese opinions).
It is true, as my good colleague Mark Ferguson noted at LabourList, that there were enough votes in the Commons to still carry intervention, if not through a standard whipping process.
But I think there is a simple reason for Cameron's reaction, and it is not petulance. I believe Cameron would have gone to considerable lengths to embark upon military action. It was that he could not continue to invest his fast-diminishing political capital in a joint venture with a partner he could not trust, after his experience in the earlier vote.
And where does that leave us? In a situation which has been botched with, sadly, the leader of my party at the centre of the botching and now talking about bringing "diplomatic, political and other pressure" to bear on Assad.
Because he's clearly really going to respond to that, right?
When the dust settles from all this, I am afraid that the historians will see this moment with Cameron in rather a positive light, as someone who tried his best in a difficult situation, but failed. And they Miliband as someone who, either through clumsiness or, worse, politicking, squandered the chances of Britain helping a benighted people in their hour of need.
As if to show the House of Commons the full horror of what it had achieved, a children's school was bombed with a napalm-like substance.
I shall probably blog about this at greater length, but for the moment I will leave you with the words of my good comrade, Nick Cohen, from today:
Can't help thinking that the British Parliament's Syrian vote will be remembered as a low and mean moment in our historyQuite.
— Nick Cohen (@NickCohen4) August 30, 2013