Definition: In this task, you need to generate an appropriate title for the given summary of some paragraph. The generated title must be short and should include the main topic of the given text. Your summary should be less than 20 words long.
Input: 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: Can its savagery be explained?