British Prime Minister David Cameron visits General Dynamics in Blackwood, Wales, on Wednesday. (Peter Macdiarmid/pool via European Pressphoto Agency)

A little more than a year ago, British Prime Minister David Cameron went to the House of Commons to seek its approval for military action against the Syrian regime. Cameron didn't need to do so – he could have declared royal prerogative and superseded parliament – but, aware that the British public felt burnt by the way the Iraq war was handled, he wanted all the justification he could get.

During an eight hour debate, Cameron made his case. “It is not about taking sides in the Syrian conflict, it is not about invading, it is not about regime change, and it is not even about working more closely with the opposition,” he explained. “It is about the large-scale use of chemical weapons and our response to a war crime — nothing else."

Cameron lost the vote 285 to 272. And while it was a relatively close vote, it was historic and humiliating defeat. British governments almost never lose votes on matters of war and national security. The last similar instance was way back in 1782, when MPs voted against continuing to fight in the War of Independence. After that defeat, then-Prime Minister Lord North resigned within a month. Clearly many felt Cameron should do the same. As the votes were read out and Cameron's loss became apparent, one MP shouted simply "resign." The British press were unanimous:

Cameron didn't resign, of course. And now, there are signs that Cameron is going to call for war again; perhaps in Syria, although not against the Syrian regime. When on Thursday asked about the potential for strikes against the extremist group Islamic State, the prime minister wouldn't rule it out. "We should pursue our national interests," he told BBC radio. There are signs that things may be progressing. Later, the BBC's James Lansdale has tweeted that Cameron's Conservative Party is asking MPs for their views on military action against Islamic State.

Cameron was rightly shaken by his Syria defeat, and the specter of Iraq still hangs over British opinion. So why would Cameron risk it all again? Cameron's gamble comes from an understanding that Islamic State has touched British society in a way few others have. The man accused of beheading American journalists James Foley and Steven Sotloff spoke with a clear London accent, and another hostage is said to be British. Hundreds of British citizens are believed to have gone to fight with Islamic State, and the group's reach has been seen in central London.

In may also factor in that the British got a taste of this particular branch of barbarity not long after the Syria vote, when two men claiming Islamist beliefs murdered and attempted to behead a British soldier in broad daylight on a London street. Public opinion now seems to support some kind of intervention – One YouGov/Sunday Times poll conducted late August showed 45 percent of the British public supported airstrikes against Islamic State, versus 31 percent who were opposed. Polls from last year found a majority of people opposed intervention in Syria.

Cameron's tone suggests caution, however. Where as Cameron seemed to be leading the calls for intervention in Syria last year, this time the United States has already targeted Islamic State. Cameron and President Obama now appear to be pushing for a stronger bilateral response to the Islamic State problem, with an op-ed authored by both in the London Times that specifically criticizes the "isolationist" approach and calls for a more robust NATO response to world disasters. It's also worth noting that so far, the suggested intervention seems likely to be limited to Iraq, where the recognized government will agree to it, and not Syria.

It's still a risk, of course. In hindsight, Cameron's defeat in the House of Commons may have been the death knell for Western intervention against the Assad regime. But hindsight also lends itself to the thinking that Western inaction in Syria may have helped Islamic State gain traction. And Cameron, up for election next year, may be wondering what sort of legacy inaction against Islamic State would leave him.