U.K. Prime Minister David Cameron (Dan Kitwood/Getty Images)

The British Parliament narrowly voted down Prime Minister David Cameron's request for approval to take limited military action against Syria, turning what was expected to be a symbolic gesture of approval into a shocking defeat.

British prime ministers are rarely defeated by Parliament on national security or foreign policy issues, making Thursday's vote not just a setback for the U.S.-led effort to punish Syria for its use of chemical weapons against civilians but a major moment for British politics. The Times of London will run a story on Friday's front page saying that Cameron was "humiliated." But this isn't about Cameron as much as it's about his predecessor's predecessor: one Tony C.L. Blair, in office 1997 to 2007.

There are any number of ways to look at the vote: as a reflection of the dim public support for yet another military engagement in the Middle East, a skepticism about following the United States into conflict and perhaps as a political failure by Cameron and his office. But one factor that surely played a tremendous role in the defeat are the ghosts of the Iraq war, which still linger in British politics.

Britain lost 179 soldiers fighting in Iraq -- a small fraction of the United States' 4,400-plus casualties. But the sense that the country was dragged, wrongly and perhaps dishonestly, into a war it should never have entered has persisted there in a way that it hasn't in the United States. And that's likely a big part of why Parliament just couldn't stomach approving intervention, however arms-length, in a conflict in neighboring Syria that already looks awfully Iraq-like.

The ghosts of Iraq were in many ways exorcised in the United States by the 2006 midterm election, taken by many as a direct rejection of the war, and especially by the 2008 presidential election. My colleague Brad Plumer wrote today about how President Obama's election was perceived within the country as such a drastic shift away from the Bush administration and the Iraq war that it ended up almost completely demobilizing the U.S. anti-war movement.

That didn't quite happen in Britain. Prime Minister Tony Blair, who was blamed in British politics for the Iraq debacle in about the same way that Bush was in the United States, resigned in 2007. But the ghosts of Iraq have not been as easy to shoo away. A very public demonstration of this came in 2009 and 2010, when the British Parliament launched what it called the Chilcot inquiry, after chairman and member of Parliament John Chilcot, a formal investigation into British government involvement in the Iraq War. The climax of the inquiry came when Parliament compelled Blair to come out of retirement and testify publicly about how and why he led the country into Iraq. It was part inquiry and part ritual humiliation, an effort to exorcise the ghosts of the war.

As Thursday's vote against Cameron showed, the Chilcot inquiry and the 10 years elapsed since the invasion of Iraq have far from healed the nation's scars from a war that made it doubt not just intervention in the Middle East but, at moments, its sense of fealty to U.S. foreign policy.

There will be a temptation in the White House to blame Cameron for mismanaging the vote on Syria. But a more appropriate scapegoat might be Blair, who left Britain with a memory of Iraq still fresh enough to scare its Parliament away from a conflict that it apparently worries could follow a similar trajectory. Still, those who warn that Syria could become the next Iraq have missed the last two years. Syria is already Iraq.