Prime Minster David Cameron kicked off the debate by telling lawmakers that "the threat (from IS) is very real." He added: "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?"
Cameron said high-precision, laser-guided Brimstone missiles would help to make a real difference by hitting the de facto Islamic State capital of Raqqa and its oil-trading business.
Jeremy Corbyn, the anti-war leader of the opposition Labour Party who was reportedly derided as a "terrorist sympathizer" by Cameron, wrote in The Guardian Wednesday: "He (Cameron) knows that opposition to his ill-thought-out rush to war is growing. On planning, strategy, ground troops, diplomacy, the terrorist threat, refugees and civilian casualties, it's become increasingly clear the prime minister's proposal simply doesn't stack up."
Yet Corbyn himself faced the biggest challenge of his few months' leadership to date, was forced to allow his lawmakers to vote according to their conscience in order to quell a rebellion in his party over the military action. Many of his party voted with the prime minister, a move which may bring into question Corbyn's leadership.
The British public is divided over launching the strikes, with a YouGov opinion poll showing voter support for action in Syria had fallen to the lowest level since September 2014, with 48 percent of respondents supporting strikes and 31 percent against.
Those opposed to air strikes recalled the events of 2003 when Britain helped the United States to invade Iraq after asserting - wrongly, as it later turned out - that dictator Saddam Hussein possessed weapons of mass destruction.