Tim Farron has reversed his position on air strikes and announced he will support David Cameron's motion to bomb ISIS in Syria.
Farron, the leader of the Liberal Democrats and a committed Christian, announced in a statement last night that he believed it was the right thing to do and urged his fellow Lib Dem MPs to support him.
"I believe it is right to support a measured, legal and broad-based international effort to tackle the evil regime that has helped trigger the wave of hundreds of thousands of desperate refugees, fleeing for their lives.
"I will therefore be asking my parliamentary colleagues to join me in the lobby to support this motion."
However less than a month ago Farron warned against air strikes in Syria calling it a "counterproductive military action."
"More and more bombs are not the answer," he said in early November. "Adding extra war will simply create a bigger stream of refugees justifiably looking to escape."
Farron acknowledged his position would be unpopular with party members, many of whom have campaigned against war in Syria.
"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," he said in his statement.
He was among a number of Lib Dem MPs who rebelled against the coalition government's proposal to launch air strikes against the Assad regime in Syria in 2013. He also voted against the Iraq war in 2003.
But in response to David Cameron's proposal for air strikes exclusively against ISIS in Syria Farron, along with a number of leading Lib Dem figures, published a list of five demands to be met before they would support the Prime Minister.
"It is my judgement that, on balance, the five tests I set out have been met as best they can," last night's statement read.
However the government has shown no indication that they will meet Farron's demands. Cameron has yet to announce when he will publish a delayed controversial report on the Muslim Brotherhood, one of the Lib Dems' key requirements.
Farron also called on the government to increase its acceptance of Syrian refugees. As yet Cameron has not said he is willing to increase the 20,000 figure he set out.
Nevertheless Farron said the motion before MPs today was "comprehensive." He did not, however, give his unreserved support and said he "will not hesitate to withdraw support" if he does not think the government continues to act "in the national interest and in the interests of the millions of Syrians and Iraqis who deserve a stable home."