Bearing down on Islamic State will require patience and persistence, David Cameron has warned, after RAF warplanes mounted their first strikes against the extremists in their Syrian heartlands.
British forces were gearing up for further attacks against the militants, with more fighter jets arriving at RAF Akrotiri on Cyprus from where the bombing missions are carried out.
The engagement by UK aircraft was hailed by France as a response to the call for "European solidarity" issued by President Francois Hollande in the aftermath of last month's Paris terror attacks which left 130 dead.
However there were bitter recriminations in the Labour Party after Wednesday night's Commons vote exposed the depths of the divisions within its ranks.
Within hours of MPs giving the green light to the extension of strikes against IS into Syria, the first Tornado GR4 fighter bombers were in the air and heading towards an oilfield controlled by the militants.
Two more Tornados and six Typhoons were subsequently despatched to the region from their bases in the UK, doubling the strike force at RAF Akrotiri.
Mr Cameron said the move would be welcomed by Britain's allies, including Muslim countries which had asked the UK to become involved, but stressed that degrading IS would take time.
"We are going to need to be patient and persistent. This is going to take time. It is complex, it is difficult what we are asking our pilots to do, and our thoughts should be with them and their families," he said.
Four Tornados carrying Paveway IV guided bombs took part in the first raids overnight, targeting the extensive Omar oilfield which is used by IS - also referred to Isil, Isis or Daesh - to help finance its operations.
In a statement, the Ministry of Defence said the jets - supported by a Voyager air refuelling tanker, an unmanned Reaper drone and other coalition aircraft - had attacked six targets.
"Carefully selected elements of the oilfield infrastructure were targeted, ensuring the strikes will have a significant impact on Daesh's ability to extract the oil to fund their terrorism," the statement said.
"Our initial analysis of the operation indicates that the strikes were successful."
Defence Secretary Michael Fallon said the operation had struck a "very real blow" at the extremists.
"The terrorists depend for their revenue on the control of oil. Cutting off their finances is extremely important to degrading the terrorists, to undermining their campaign in Iraq, and to shrink their operations in eastern Syria," he said.
Meanwhile, Labour MPs who ignored calls by party leader Jeremy Corbyn to oppose further military action in Wednesday's vote complained they were being subjected to online bullying and threats of de-selection by pro-Corbyn activists.
Shadow leader of the Commons Chris Bryant called for a security review after a number of MPs had their offices barricaded by protesters while others were sent photos of dead babies and severed heads.
The 66 Labour MPs who voted with the Government included shadow foreign secretary Hilary Benn whose powerful appeal for actions against the IS "fascists" drew a rare round of applause for MPs on both sides of the House.
However shadow chancellor John McDonnell - Mr Corbyn's closest Shadow Cabinet ally - poured cold water on his speech, saying it reminded him of Tony Blair's speech taking the country into the Iraq War.
"I am always anxious that the greatest oratory can lead us into the greatest mistakes," he said.