The US attack on Syria is haunted by the ghost of Iraq.
"It's a bit like being present after a massive explosion. There is broken glass and dust is wafting around everywhere. It will take time for the dust to settle". This is how a senior Tory MP described the mood in the party in the wake of the defeat of the government's motion paving the way for military action on Syria.
It was a devastating blow to David Cameron's authority - the veteran Tory journalist Max Hastings writing in the Daily Mail called it a "savage defeat" for the prime minister. It was made all the more humiliating since Cameron had already offered a compromise by agreeing that there would have to be a further vote before any missiles were actually launched.
Cameron had confidently told Obama the weekend before that Britain would join him in an attack on Syria. It is unlikely that Britain's military role was crucial, but it would have provided essential political cover to the US president. Cameron's defeat left Obama dangerously isolated, especially in the face of a US public unconvinced of the case for war.
He was forced to delay seemingly imminent airstrikes and gamble on winning the approval of Congress before taking any action. This in turn suddenly put more pressure on French president Francois Hollande who had also signaled support for bombing, to put it to a vote in the French parliament.
Why did Cameron lose the vote - and why did he then immediately announce that Britain would stay out of any attack despite the fact that Labour's position was not one of opposition to military action in principle?
The legacy of the huge protests over Iraq in 2003 was crucial. And there is a widespread feeling that subsequent events - the absence of Blair's fabled Weapons of Mass Destruction, the huge death toll, the massive armed resistance to the US and British occupation and failure and the continuing violent instability in Iraq - vindicated the anti-war movement and not the warmongers. As Cameron was forced to bitterly acknowledge in the parliamentary debate over Syria, Iraq has "poisoned the well of public opinion".
Indeed, one reason Cameron has been so keen to intervene abroad is the desire to overcome the "Iraq syndrome" and re-assert the capacity of the British and other Western states to wield military force abroad. So over Libya, it was the British and French that took the initiative (even if they then found that they had to largely rely on US air power) and over Syria, Cameron has been pushing Obama to take stronger action for months.
Secondly is the fact that Western imperialism suffered major defeats in both Iraq and Afghanistan. Indeed Obama's whole presidency has reflected this. A key aim has been to extract the US from land wars in the Middle East. It has also shaped the US policy towards Syria. Contrary to those you argue that the US has decisively shaped the insurgency against the Assad regime, US policy has been marked by hesitancy and a reluctance to intervene, not least because of fears about its ability to control what might follow the regime's defeat.
This fear is not simply restricted to the Saudi and Qatari backed jihadis fighting the Assad regime but also those forces, mostly around the opposition Free Syrian Army, that continue to express the revolutionary impulse that lay behind the initial uprising against the regime. As recently as May, John Kerry, the US secretary of state met with Sergei Lavrov, Russia's foreign minister, to see if they could agree a plan for a "transitional government" that might include elements of the current Assad regime.
Obama's announcement last year of "red lines" that would trigger a US military response if crossed - notably the use of chemical weapons - were fuelled by a desire to stay out of Syria while appearing tough. When claims surfaced earlier this year about potential chemical weapons use, Obama played this down and now said the US would only act over "systematic" use of such weapons.
Confronted with a chemical weapons attack on a much greater scale, Obama was faced with the danger that if the US did nothing it would expose it as weak. But Obama's talk, at least so far, has been of a "narrow and limited" action that would be a "shot across the bows" of the regime.
In Britain too, a succession of former generals lined up to stress the dangers of intervention, including Lord Dannatt, the former head of the British army. Britain suffered military defeats in both Iraq and Afghanistan and clearly sections of the ruling class have little appetite for risking entanglement for no clear gain. In Libya too, though Gaddafi was overthrown the West has so far failed to create a stable and reliable successor regime.
This combination of ruling class divisions and popular hostility proved decisive. Labour leaders Ed Miliband's initial willingness to support an attack gave way, in the face a growing internal revolt, to calls for a series of conditions to be met before Labour would back any intervention. Though hardly a conversion to an anti-imperialist position, it was enough to fracture the usual bi-partisan consensus among party leaders on foreign policy and war in a way not seen the Suez conflict in 1956.
This was of huge significance. It allowed a much greater space for the popular mood to express itself. Despite all the main parties being in principle in favour of attacks, the end result was Cameron ruling out any involvement. The Labour MP Ben Bradshaw observed, "the Commons voted against Britain taking military action by accident. It may be an outcome supported by a majority of the public, but it was not what any of the main parties or their leaders wanted".
Though touted as a triumph for parliament's credibility, it was really a victory for the extra-parliamentary mass movement of 2002-04 and the huge mood of opposition today to action against Syria. Cameron's government has emerged from this much weaker. This increases the potential to derail it on other fronts and underlines the urgency of rebuilding a fightback against the government's austerity programme.