Terror threat

Since the sudden appearance of the extremist Sunni Islamic State (IS), the group has seized headlines with a shocking level of blood-letting and cruelty - but can its savagery be explained, asks Fawaz A Gerges.

Islamic State has become synonymous with viciousness - beheadings, crucifixions, stonings, massacres, burying victims alive and religious and ethnic cleansing.

While such savagery might seem senseless to the vast majority of civilised human beings, for IS it is a rational choice. It is a conscious decision to terrorise enemies and impress and co-opt new recruits.

IS adheres to a doctrine of total war without limits and constraints - no such thing, for instance, as arbitration or compromise when it comes to settling disputes with even Sunni Islamist rivals. Unlike its parent organisation, al-Qaeda, IS pays no lip service to theology to justify its crimes.

Islamic State: Can its savagery be explained?