South Lakes MP Tim Farron is among MPs to have voted for military action in Syria, paving the way for bombing raids against Islamic State targets.
The Government plans were approved by 397 votes to 223 - a majority of 174.
67 Labour MPs backed airstrikes - 10 abstained. During the debate, Mr Farron - the Liberal Democrat Leader, declared his intention to vote for military action.
In an open letter to The Liberal Democrats before the vote, he wrote: "The decision every politician dreads is whether or not to send brave servicemen and women into military action in defence of our country.
"When the Government asked MPs to support extending airstrikes into Syria in 2013 to target Assad, I refused to provide that support.
"I was not convinced at that time our intervention was properly effective, nor that it would be backed by a diplomatic effort to establish a lasting peace or prevent more suffering than it caused.
"I believe it is right to support what is a measured, legal and broad-based international effort to tackle the evil regime that has contributed to the hundreds of thousands of desperate refugees, fleeing for their lives.
"As a Liberal Democrat I am an internationalist.
"I believe in acting collectively with our friends and our European allies, joining Germany, France, Denmark, the Netherlands and others in responding to threats to our security within a framework of international law.
"I was a proud supporter of Charles Kennedy when he led his MPs into the lobbies against an illegal war in Iraq on the basis of a dossier that sought to contrive a threat where none existed.
"This war has cast a long shadow over Britain's role in the world and has severely damaged the confidence that the British people have in our intelligence services and the decisions of our Prime Ministers.
"But this is not Iraq.
"The Liberal Democrats were also the first party to call for action in Bosnia and Kosovo led by Paddy Ashdown. We call for action again now. The threat to Britain and our allies is clear. We can and must play a part to extinguish ISIL.
"I am well aware that many in the party will disagree with me. I hope that, even if you cannot support me, you can support the approach I have taken and recognise that I have taken this difficult decision after the fullest consideration."
British service men and women will now be in harm’s way and the loss of innocent lives is sadly almost inevitable pic.twitter.com/z338VAmIai
— Jeremy Corbyn MP (@jeremycorbyn) December 2, 2015I believe the House has taken the right decision to keep the UK safe - military action in Syria as one part of a broader strategy.
— David Cameron (@David_Cameron) December 2, 2015