The brutality of the Islamist fighters rampaging across northern Syria and Iraq attracted little attention outside the region until images of their cruelty began circulating on social media. Two photos involving Westerners got the world clamouring to do something about the threat to the Middle East and beyond posed by the Sunni Muslim group Islamic State. The beheading of American journalist James Foley by a masked man presumed to be British, and the son of an Australian jihadi holding up a severed head, caused shock, outrage and fear. After months of near silence, there is condemnation, meetings and calls for action.

There should have been no surprise. The cruelty and extremism of those behind Islamic State had been often recounted by those forced to live under its rule. People who refuse to follow or are considered enemies are executed or buried alive. Perversely, images of the killings posted on recruiting websites have attracted thousands of foreigners, mostly from the Middle East and North Africa but also hundreds from Europe and moderate Muslim countries like Indonesia and Malaysia. The draw is the group's dream of creating a global caliphate and its rapid progress in moving towards that goal. After little more than a year of fighting, it holds one-third of Syria and Iraq, despite recent losses from limited American air strikes in Iraq's Kurdish north to protect ethnic and religious minorities.

But the United States and its allies are limited by what they can achieve, particularly in civil-war-wracked Syria. The most viable approach is to train soldiers and for the Iraqi government to adopt an inclusive policy towards all tribal, ethnic and religious groups. But that does not stop the threat of foreigners fighting for Islamic State returning home and spreading their extremist views. One plot has already been uncovered in Malaysia and Susilo Bambang Yudhoyono, the outgoing president of Indonesia, the world's most populous Muslim country, has called on Islamic leaders to unite against extremism. In Europe and Australia, where dozens of nationals are known to have joined Islamic State, officials are debating strategies.