Judy Woodruff:

Only one pocket of resistance to the ruling Assad regime remains in Syria. And since late last year, Bashar al-Assad's military, backed by Russia, has been pounding Idlib province relentlessly.

Now, nearly one million people are on the move in the freezing cold and out in the open.

As Nick Schifrin reports, in a war defined by displacement, this is the largest movement of people of the entire war.