President Bashar al-Assad's army is mercilessly shelling the city of Homs for the 20th day in a row in Syria. And there are signs of escalation in violence across the country. Activists say Syrian troops are using helicopter gunships to strafe mountain villages where anti-regime rebels could be hiding. There are also reports of Syrian forces now staging vicious door-to-door raids in Damascus. Joining the program is Jim Muir, correspondent for our partner the BBC.