But on a day meant to convey national unity, Cameron struggled to even get through his opening remarks, as outraged opposition Labour Party lawmakers demanded he retract remarks reportedly made at a closed-door meeting in which he branded opponents a "bunch of terrorist sympathizers."
Lawmakers demanded an apology as the 10½-hour debate got underway in the House of Commons, arguing the comment showed a lack of respect to those who disagreed with Cameron's policies.
The last-minute dispute threatened to erode the comfortable majority Cameron was relying on when he sought to authorize the Royal Air Force to launch airstrikes against suspected positions in Syria held by the Islamic State group, also known as ISIS, ISIL and its Arabic acronym, Daesh. Britain is already part of the US-led coalition, but has restricted its actions to Iraq.
"This is not about whether we want to fight terrorism, it's about how best we do that," Cameron said. "The question is this: Do we work with our allies to degrade and destroy this threat and do we go after these terrorists in their heartlands, from where they are plotting to kill British people? Or do we sit back and wait for them to attack us?"
British officials say this could reduce civilian casualties.
But any measure is politically loaded in Britain because many lawmakers fear revisiting the chaotic situation that occurred in the Iraq war, in which 179 UK service personnel died.