Parliament has voted to begin air strikes over Isis territory in Syria as well as Iraq. The first two fighter jets left their base just hours after the decision was taken on Wednesday.
MPs voted by 397 to 223 votes after a ten-hour debate, but reportedly many Labour MPs, given a free vote by party leader Jeremy Corbyn, were still making up their minds throughout the day whether to support military intervention in Syria's civil war.
Hilary Benn, shadow foreign secretary, was one of the last speakers in the marathon debate. He defied Corbyn's wishes for the party to vote against air strikes in a stirring speech.
... I hope the House will bear with me if I direct my closing remarks to my Labour friends and colleagues on this side of the House. As a party, we have always been defined by our internationalism. We believe we have a responsibility one to another. We never have and we never should walk by on the other side of the road.
And we are here faced by fascists. Not just their calculated brutality, but their belief that they are superior to every single one of us here tonight, and all of the people that we represent. They hold us in contempt. They hold our values in contempt. They hold our belief in tolerance and decency in contempt. They hold our democracy, the means by which we will make our decision tonight, in contempt. And what we know about fascists is that they need to be defeated.
And it is why, as we have heard tonight, socialists and trade unionists and others joined the International Brigade in the 1930s to fight against Franco. It’s why this entire House stood up against Hitler and Mussolini. It is why our party has always stood up against the denial of human rights and for justice. And my view, Mr Speaker, is that we must now confront this evil. It is now time for us to do our bit in Syria. And that is why I ask my colleagues to vote for this motion tonight.
Benn's speech was credited with swaying the votes of several MPs at the 11th hour. In total, 66 Labour MPs voted with the government.
Benn's oratory immediately drew comparisons with the speeches of his father, the hero of the Labour left, Tony Benn.
Earlier in the day, Mhairi Black, the SNP MP for Paisley and Renfrewshire South and the youngest sitting MP, tweeted a video of a famous Benn senior speech in the Commons before a vote on whether to sell arms to Iraq in 1992, after the first Gulf War.
In it, he spoke movingly of his experiences of WWII as a child (Interestingly, Corbyn can be seen sitting behind him.)
The speeches given by both father and son are strikingly similar in their passion and eloquence, but couldn't be more different in their views on warfare:
War is an easy thing to talk about. There are not many people of the generation that remember it here... I was in London in the Blitz in 1940.
Every morning, the Docklands on fire, 500 people killed in Westminster by a landmine one night, it was terrifying. Aren't Arabs terrified? Aren't Iraqis terrified? Aren't Israelis terrified? Don't Arab and Israeli women weep when their children die? Doesn't bombing strengthen their determination?
What fools we are, to live in a generation, for which war is a computer game for our children, and just an interesting little Channel 4 News item.
Every member of parliament tonight that votes for the government motion will be consciously and deliberately accepting your responsibility for the deaths of innocent people, if the war begins as I fear it will.
The words of [the founding UN charter] are etched into my mind and move me even as I think of them. 'We the people of the United Nations determine to save future generations, succeeding generations, from the scurge of war which twice in our lifetimes has caused untold suffering to mankind.
That was the pledge of that generation, to this generation, and it will be the greatest betrayal of all if we vote to abandon the charter and take unilateral action and pretend we are doing it in the name of the international community.
Speaking on Radio 4's Today programme on Thursday morning, shadow chancellor John McDonnell delivered a masterful backhander to Benn, saying that the shadow foreign secretary's speech reminded him of none other than Tony Blair before the 2003 invasion of Iraq:
I'm always anxious that the greatest oratory is going to lead us to the greatest mistakes.