LONDON -- Humiliated by lawmakers over Syria, Prime Minister David Cameron of Britain seems destined to cut a lesser figure, weakened both at home and abroad by a self-made debacle that has also highlighted his war-weary country's reluctance to get involved with another American project in the Middle East.
No British prime minister in memory has sought and failed to win support from his legislators for military action, and the rebuff of Mr. Cameron late Thursday means the United States will have to intervene without its closest security and intelligence ally. In a reversal of the situation in Iraq, it may be France, Britain's neighbor and rival, that gives European military and political cover to President Obama.
In the wake of the shocking parliamentary defeat, Mr. Cameron's closest political friend, the chancellor of the Exchequer, George Osborne, conceded that the vote would provoke a period of "national soul-searching" about Britain's role in the world. But he also cautioned against exaggerating the impact of the vote. "I hope this doesn't become a moment when we turn our back on all of the world's problems," he said.
The growing isolation of Britain appears on the European level, too. After more than a decade of involvement in conflicts -- and ground down by a weak economy -- the British public is increasingly skeptical about its membership in the European Union, whose single currency is just starting to recover from a near-death experience.
Some of those Conservative politicians most critical of the European Union seem also to have little faith in the other pillar of Britain's postwar foreign policy -- its "special relationship" with the United States.
The Labour Party leader, Ed Miliband, put it this way to the BBC: "I think being an ally with 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."
Calling the reluctance to use military force abroad "a pretty profound change," Malcolm Chalmers, research director at the Royal United Services Institute in London, which specializes in defense and security policy, said, "It has the feeling of the post-Vietnam change in the United States."
Mr. Chalmers saw "a disconnect between the political elite and the public," adding: "It's there on military intervention, it is certainly there on Europe and on immigration. There is a sense among the British public that we should look after ourselves rather than other people."
In fact, the events that unfolded during the week were shaped by prosaic political miscalculation, with the leaders of all three main political parties misjudging the public mood and losing control of their parties. Mr. Cameron was probably encouraged by the fact that British lawmakers had supported military intervention in Libya in 2011, and thought he had a compromise deal with Mr. Miliband, for example, who discovered that his backbenchers would not accept it. In the end, both Mr. Cameron and Deputy Prime Minister Nick Clegg, leader of the Liberal Democrats, found themselves unable to keep their legislators in line, even on an essentially meaningless motion that authorized nothing.
Even if, in several months, it turns out that recent events have saved the country from an unwise military intervention, that will be of little comfort to Mr. Cameron. In those circumstances, his political opponents will be able to cast further doubt on the prime minister's judgment and claim that they -- not he -- deserve the credit for averting another foreign policy misstep.
The experience of Iraq hung over the debate. With a public discussion about the intelligence assessments, the work of United Nations weapons inspectors and the legal case for military action, few could miss the parallels with the invasion of Iraq. That war wrecked the premiership of the former Labour Party leader, Tony Blair, who was ridiculed as Washington's poodle and accused of misrepresenting intelligence about Saddam Hussein's supposed possession of weapons of mass destruction.
Even before military action in 2003, the prospect of invading Iraq was unpopular in Britain, with as many as one million protesters marching in opposition at one point. Mr. Miliband had not yet been elected to Parliament, and the fact that he never voted for military action was an important element in his campaign to become party leader.
Mr. Cameron was all too aware of the legacy of Iraq. His decision to recall Parliament from vacation, and to publish legal advice on the case for action and the intelligence assessment, were intended to demonstrate transparency and underline the difference between him and Mr. Blair.
Initially, Mr. Cameron wanted authorization for limited military strikes. After discussions with Mr. Miliband, he was forced to retreat, ending with a bland motion that promised a second vote after United Nations inspectors in Damascus had completed their work.
To the fury of Mr. Cameron's office, Mr. Miliband could not deliver in the face of hostility from Labour legislators. Many of them remembered being persuaded against their better judgment to support Mr. Blair on Iraq and, now in opposition, were in no mood to do Mr. Cameron a similar favor.
The anger over Mr. Miliband's stance surfaced after his speech when one Cameron aide -- identified by the Labour Party as the director of government communications, Craig Oliver -- agreed, in response to a question from a reporter, that Mr. Miliband had given "succor to Assad."
But Mr. Cameron also has problems within his own party. There is rumbling discontent among a minority of Conservatives over his leadership, particularly among those never reconciled to joining a coalition government with the Liberal Democrats.
The vote also reflected the diminished international status of Mr. Obama, who no longer enjoys the benefit of the doubt on foreign policy that existed at the start of his first term, Mr. Chalmers said. "After Iraq and Afghanistan, there is much more questioning about the role of military force in discretionary operations in the Middle East," he said.
Nigel Sheinwald, a former British ambassador both to Brussels and Washington, said there would be some damage to Britain's standing, but nothing irreparable. "There is no doubt that in any alliance reliability, dependability and predictability are all key facets," he said. "Britain will have to find a way of restoring that reputation."
But Mr. Sheinwald said that many of the issues raised in Britain will be familiar to President Obama from the American debate. "Syria was an issue on which the West has struggled to get a coherent policy for the last two and a half years," he said. "I don't think it is going, necessarily, to be the model for the future any more than Libya was."
Alan Cowell contributed reporting.
This article originally appeared in The New York Times.