(CNN) -- David Cameron must have whiplash. Practically overnight this week, the British prime minister went from being one of the leading voices demanding that Syria's President Bashar al-Assad be punished for using chemical weapons, to a humbled, chastened politician with his hands tied. 

British lawmakers voted Thursday night against even the possibility of using force against Syria, forcing Cameron to concede bluntly, "We will not be taking part in military action." 

What do Syria's neighbors think? 

The vote was close -- seven MPs out of the 557 who voted could have changed the result -- and the outcome was a shock. Prime ministers aren't supposed to lose votes on the use of military force. British media said it hadn't happened in hundreds of years. 

But although the result was stunning in one sense, in another it wasn't surprising. 

Over more than seven hours of debate on Syria loomed one chilling specter: Iraq. 

Bergen: Syria is a problem from hell for the U.S. 

Britain feels badly burned by the way Tony Blair led the country into war there a decade ago, and Cameron was fighting a defensive battle against the memory of Blair from the moment he kicked off debate in the House of Commons: "I'm deeply mindful of the lessons of previous conflicts, in particular the deep concerns of the country of what went wrong in Iraq. We're not invading a country; we're not searching for chemical weapons." 

It's an argument he needed to make. 

Why Russia, China, and Iran are standing by Syria 
Are his hands tied?
ian w