A UN observer photographs the bodies of some of those killed in Houla. Reuters/Shaam News Network

As images of the victims of last week’s Houla massacre were broadcast around the world, and the stories of their deaths began to be told, the wave of outrage and horror in the international community gained force. The White House denounced an act of “unspeakable and inhuman brutality”; the UK foreign secretary spoke of an “appalling crime”; the UN security council condemned the “outrageous use of force against [a] civilian population”, and said it constituted a “violation of applicable international law”.

Yet for all this, the next step is troublingly unclear. The killing of 108 civilians, among them 49 children, was only the latest in a series of atrocities that have taken place under the regime of Bashar al-Assad in Syria in the past 14 months. More than 9,000 Syrians are thought to have died in this period, including members of the security forces or suspected regime sympathisers who were killed by the armed opposition. While UN envoy Kofi Annan says that a “tipping point” in the crisis has now been reached, the UN security council itself remains hindered by the positions of Russia and China, both of whom have dug in their heels against external intervention. So what are the arguments for and against action, and what form could it take? Read more