This is a victory for the anti-war movement - not just our recent campaigning on Syria but, even more importantly, the legacy of over a decade of opposition to the 'war on terror', especially the huge wave of protests against war in Iraq.
Parliament has finally - under the weight of long-term pressure - come close to reflecting public opinion.
It is a landmark event in the history of UK foreign policy: the exact repercussions are not clear, but it creates an opening that the movement can use to challenge the 'special relationship' with the US. The long-term strategic aim of the Stop the War Coalition - to break British foreign policy from slavish allegiance to the US - is suddenly more plausible.
It also creates a severe political crisis for David Cameron personally and for the government, with profound consequences beyond the specific issue of Syria. The government suddenly appears weak, while its opponents are emboldened. Above all, this provides an opportunity for the anti-austerity movement to hit back against a weak government led by a prime minister whose authority is in tatters.
The parliamentary vote also puts great pressure on Barack Obama to retreat from launching a military assault on Syria. But he may still go ahead - perhaps as early as this weekend. Saturday's national demonstration in London is therefore tremendously important: we need to stop this war altogether, while driving home the movement's achievement in creating such a crisis for our government.
Those on the left who have remained dedicated to building Stop the War Coalition have been vindicated. Our longstanding view that war and imperialism remain live political questions of great importance in this country is demonstrably correct.
It is the question of war that is now shaking British politics and raising speculation about the prime minister's future. For deep-seated political reasons, war will continue to be a central issue and the anti-war movement must remain a priority.
Here is the statement from the Stop the War Coalition:
'The Stop the War Coalition welcomes the defeat of David Cameron’s plan to attack Syria in parliament tonight.
We didn’t stop the war in Iraq, but we did create a mass anti war opinion in Britain. That tide of anti war opinion has made itself felt in the past few days.
MPs have in their majority refused to back a fourth intervention by western powers since 2001. They have for once reflected the majority public opinion in this country.
We now have to reject all attempts at intervention in Syria and to develop a foreign policy which is based on equality and justice, and the rights of national sovereignty.
The Tory led government will try to recoup the situation. We will demonstrate on Saturday against this intervention, whether by the US alone or with Britain involved. It is the aim of the anti-war movement to ensure that the US is forced to abandon the attack on Syria now that the country with which it is supposed to enjoy a ‘special relationship’ has carried a parliamentary vote against war.'