The outcome is especially bizarre because Prime Minister David Cameron of Britain joined President Francois Hollande of France in strongly pushing US President Barack Obama to act more boldly in Syria - to provide arms to the rebels, to consider a no-fly zone, to strike hard in response to the alleged use of chemical weapons.

Cameron's activism far outstripped Britain's teamwork with the US on the Iraq war, for which bitter Britons referred to prime minister Tony Blair as president George W. Bush's poodle.

"On this issue Britain wasn't Obama's poodle but his Rottweiler," said Robin Niblett, the director of Chatham House, the Royal Institute of International Affairs.

"We and the French were pushing Obama on Syria to arm the opposition, lift the embargoes and strike back."

Vincent Desportes, a retired French general and former director of the School of War, said: "The United States and France are truly in the same boat, in the same difficulty, and this difficulty is that of the credibility and place of the West in the world."

For France, he said, it is an occasion to tell the Americans that "we weren't with you in Iraq because we didn't believe in it, but now we are going with you because we do".

Britain, however, has degraded its position and credibility, he said. While France is reasserting its claim to be a global power, Britain, he said, appears to be stepping back.

The British-French turnabouts raise questions about whether the European strategic landscape has changed, especially after both Britain and France led the way in Libya in 2011 and the French took on the fight against al-Qaeda and its associates in the former French colony of Mali this year.

For Niblett, the answer is no for the French, but less clear for the British. "If there were one place in the world where the French would go along with the United States," he said, "it would be Syria," a former French mandate territory next to Lebanon.

Paris has been forceful in demanding that Iran live up to United Nations Security Council resolutions on the nuclear issue and believes in defending international norms, such as the nuclear Non-Proliferation Treaty and the Chemical Weapons Convention. "And this is limited," Niblett said. "This not a George W. Bush let's remake the Middle East moment and would represent a strong defence of an international treaty and norms on chemical weapons."

As for Britain, however, he is more troubled, while saying Cameron's defeat in Parliament was partly self-inflicted and came from bad management of his majority. "This reflects a deep scarring from Afghanistan and Iraq, where British forces were key and fought hard.

"There is a strong view in the commentariat, perhaps not a majority, that says that we can't fix these bloody, intractable problems in the Middle East so why are we trying to do it?"

Still, he said, "For the UK to step back from being the US wingman on deterrence issues is important."

Jonathan Krause, a lecturer in strategic studies at the Royal Air Force College, said people "underestimate how important France has been as a military force in the Mediterranean and in its fight against Islamism in Mali", he said.

"The French did a lot of heavy lifting in the operation in Libya. Combined with successful operation in Mali, this seems to have emboldened them.

"France is no longer as isolationist or Gaullist as they were a decade ago - there seems to be a renewed French effort to fulfil their desired role as a major European power," Krause said.