This is the BBC.

Welcome to the briefing room with me, David Aronovich.

You open the auditory door, you come on in, and find out what's going on in the world.

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beginning. If you enjoy this, you might enjoy other editions of the briefing room. Two weeks ago,

for example, we looked at whether we'd be willing to pay more tax to fund the NHS.

In this edition, with Turkey, Russia, Iran and the United States all active in the war in Syria,

I'm getting briefed on what the end game might look like.

Well, it began mid-afternoon.

Live footage from the border was showing black plumes of smoke rising above Afrin,

which is this enclave just across the border under the control of the Kurdish militia there, the YPG.

Turkish F-16 fighter jets pounding Afrin from the sky,

pounding targets from the sky.

And then on the ground,

there have been Syrian rebel fighters backed by Turkey as part of this offensive.

This week, Turkey invaded northwest Syria to fight the Kurds.

It was another twist to the Syrian Civil War, the conflict, which has been the signal disaster of the last decade, but which is supposedly nearing its end.

Over the seven years of war, the United States, Turkey, Russia and Iran have become increasingly important, either taking part

directly or else supplying and equipping favoured groups. And these powers will, between them,

shape the eventual outcome. So what I want to know today is what they want and how their

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