By Andrew Osborn
LONDON (Reuters) - He lost by just 13 votes, but Prime Minister David Cameron's failure to win parliamentary approval to launch military action against Syria may place a question mark over Britain's role in the world as well as his own career.
Cameron's inability to determine Britain's foreign policy and join Washington and Paris in strikes against Syria will strain the "special relationship" with the United States - the foundation of Britain's global role since World War Two.
It is a stunning reversal in international affairs, after a decade in which Britain was the only major power to join the United States on the battlefield in Iraq, and by far its most important comrade in arms in Afghanistan.
More than 600 British troops have died under U.S. command in those two wars, since Prime Minister Tony Blair declared he would stand "shoulder to shoulder" with America after the September 11 2001 attacks on the United States.
No more. After Cameron lost Thursday's vote to support the principle of military action against Syria to deter President Bashar al-Assad from using chemical weapons, Washington can no longer rely on Britain for automatic military backup.
"I think there will be a national soul-searching about our role in the world and whether Britain wants to play a big part in upholding the international system," said George Osborne, Cameron's Chancellor and close ally. "Obviously, it would be better from the point of view of the special relationship if we were able to take part in any military action."
There were lively scenes in parliament's wood-panelled debating chamber as MPs digested the result. One minister was seen repeatedly shouting "disgrace" at those who voted against Cameron, saying they had given "succour" to Assad.
Loud cries of "resign resign" rang out from opposition Labour lawmakers before Cameron, visibly shaken, told parliament he would heed parliament's will: "I get it".
Historians dusted off old books to find a precedent. It was the first time a British prime minister had lost a vote on war since 1782, when parliament conceded American independence by voting against further fighting to crush a colonial rebellion.
Labour's Ed Miliband - who led the parliamentary revolt saying he was not opposed to force in principle but unconvinced by Cameron's case - was the first opposition leader to oppose government plans to deploy troops since the 1956 Suez crisis.
Back then, Britain and France tried to intervene in Egypt without U.S. support. Their failure was seen as proof that post-war Britain, which had given up its global empire, could now shape world events only by standing with its superpower ally.
Paddy Ashdown, a former international envoy to Bosnia and now a member of Britain's upper house of parliament, echoed many in Britain's divided political establishment in lamenting the erosion of British influence on the world stage.
"In 50 years trying to serve my country I have never felt so depressed/ashamed," he said. "Britain's answer to the Syrian horrors? None of our business! We are a hugely diminished country."
But others said it was about time Britain gave up its great power airs and accepted the limits of its role in the world.
"The desire to re-order foreign states - still embedded in parts of the British establishment - has long been subsumed in the constitution of the U.N. and international courts of justice," wrote Simon Jenkins in the Guardian. "Sometimes it takes courage to conclude of foreign conflicts that we can only do more harm than good by meddling in them."
NO MORE POODLE
Cameron said he hoped President Barack Obama would understand, and he had nothing to apologise for.
"(This is) a government and a parliament that is deeply engaged in the world," Cameron said. "We've the fourth largest military in the world and one of the best diplomatic networks any country has in the world. We have great strengths as a country and we should continue to use those."
For Miliband - whose first act as Labour leader in 2010 was to repudiate the party's support for the Iraq invasion - the stance distanced him from Blair, the former Labour prime minister whose support for U.S. wars saw him depicted savagely in political cartoons as George W. Bush's snarling pet poodle.
"Being an ally of the United States and having a special relationship with the United States cannot simply be about doing what the American president says he wants you to do," Miliband said. "We will have disagreements with the United States, we will take a different view to them but we have got to operate on the basis of the British national interest."
Domestically, the defeat was the heaviest Cameron has suffered in his three years in power. It underlined his failure to pacify malcontents in his ruling Conservative party who complain he doesn't listen to them.
He had begun to recover from previous party rebellions over gay marriage and Britain's EU membership, had begun to erode Labour's opinion poll lead, and, with the economy showing signs of recovery, was optimistically eyeing re-election in 2015.
But 30 of his 304 Conservative MPs rebelled against him and many others used a febrile debate on the subject to criticise him and the government for trying to rush into war.
Cameron's critics are already circling. Their main allegations: He is not a conviction politician and fails to prepare the ground properly for his policies.
Public opinion was never on his side: a YouGov poll published on Thursday showed 51 percent of the British public opposed a missile strike, with just 22 percent in favour of it.
Cameron cut short his holiday to recall MPs for what he thought was going to be a swift joint strike on Syria, and tried to woo his own members of parliament before the vote.
His plan began to unravel on Wednesday evening when Miliband said he wanted major concessions before he could support action.
Cameron agreed to wait for a report from U.N. inspectors on last week's suspected chemical attack in Syria before launching any strikes, and to hold two votes in parliament instead of one.
But Miliband, battling to establish his leadership credentials within his own party, said he still couldn't back Cameron, leaving the prime minister relying solely on his own party and his Liberal Democrat junior coalition partners.
Nine of 55 LibDems joined the 30 Conservatives in rebelling. Cameron lost the motion by 285 to 272 votes.
"Were there question marks over his tactics and did they fail? Well yes, obviously," one Conservative MP who voted against Cameron told Reuters.
Cameron himself said he regretted that it hadn't been possible to build a consensus but said he had "worked hard" to try to achieve one and he thought the whips - party vote enforcers - "did do a good job".
Government fury at Miliband's stance boiled over into language normally unspoken in parliament. A national newspaper reprinted an extravagant expletive-laden tirade from a source in Cameron's office denouncing the Labour leader.
A top Cameron aide accused Miliband of "giving succour" to Assad. The Labour leader demanded the accusation be withdrawn, but Defence Secretary Philip Hammond later repeated it.
Miliband said the vote defeat had exposed Cameron for the "reckless" and "cavalier" leader that he was.
Political allies believe Cameron will recover and his party leadership will not be challenged before the election. However, critics, some in his own party, think he is now vulnerable.
David Hartwell, a former British Ministry of Defence official, told Reuters Cameron had badly miscalculated.
"Cameron really only has himself to blame. He's tied himself in a bunch of knots largely out of a desire to distance himself from his predecessors," he said, referring to Blair.
"You can't march your troops up to the top of the hill and then down again like that. He's made so much noise on Syria on strikes and chemical weapons and arming rebels and at the end of the day he's just been totally unable to deliver."
(Additional reporting by William James, Peter Apps and Costas Pitas; Editing by Guy Faulconbridge and Peter Graff)