David Cameron will stand at the dispatch box today as a war leader, a changed man. He inherited conflicts in Afghanistan and Iraq, but now he has taken the personal step to commit British forces to the frontline in another foreign field.
The beginnings of conflicts are fraught affairs and, as the old generals say, once you start bombing it's difficult to know where things will end up. Foreign conflicts have overtaken many British leaders in the past, in the recent past even, so this is a moment of personal danger for Cameron too.
After a very shaky political start Cameron has emerged ahead of the curve at the end of this week. His early insistence on pressing for a no-fly zone looked like the over-reaching ambition of an international amateur and the drafting of a UN motion, without the usual diplomatic daisy chain of phonecalls, looked almost designed to fail.
However, Cameron now looks like he has what he wanted - whether he wanted it or not. There is, Downing Street is saying, the possibility of a vote in the Commons today but you would expect, with a UN resolution in place, that the disgruntled Tories will fall in behind the leadership and that the opposition will be supportive.
Cameron will be unable to say exactly what will unfold over the next few days but he will be emphasising what Libya is not - it is not Iraq, it is not boots on the ground, it is not unilateral action outside the United Nations.
But if British lives are lost, in what the right-wing will say is a war that is not in British interests, then he could be in great trouble.
Eleven months into his premiership, exactly eight years to the day from that fateful Commons vote backing the invasion of Iraq, Cameron now really has to prove his mettle as a Prime Minister.
The Ipsos-Mori polling yesterday appeared to elevate Cameron above party politics - people like him but not his party - and that's where every Prime Minister wants to be. Finally finding his footing on the international stage, in the midst of what seems like an escalating international situation, might be the making of him.
But the domestic blowback of action in Libya could be massive. People will be stretching for the trigger of the fuel hose first thing this morning, and a spike in petrol prices might only be the first effect of the Libyan crisis. An unraveling of the Strategic Defence and Security Review could also be on the cards, given the amount of cut-threatened assets we are throwing at the situation.
The sheer uncertainty of the world viewed through the prism of 24-hour news could shake consumer confidence and economic recovery. The next quarter of economic figures come out the Wednesday before the Royal Wedding, which tonight feels like a distraction from grave matters rather than a focus for celebration
Meanwhile Barack Obama - hope, remember that - has come out of this week looking like a vacillating world policeman. It was only when the US finally threw its weight behind the UN resolution that things really began to move with, for diplomatic stage, very rapid speed.
Maybe the US felt it was more productive to hold back, so that there could be no anti-American coalition or maybe Obama was trying to get the US back to an era where it spoke softly and carried a big stick, but it seemed that America spoke with several diplomatic voice in the last week. From today, all the world leaders will be judged by actions, not words.