Confronting ISIS

The constant clamour over Muslim extremism since 9/11 makes it hard to recall the days when terrorism and revolution were practically interchangeable terms. The “r-word” has always retained some tenuous ­connection with hardcore left-wing politics in a connotative way, and groups such as Germany’s Baader Meinhof gang (later the Red Army Faction) of the 1970s and ’80s were just left-wing groups that insisted on the violent expression of revolutionary ideals. Today’s terrorists appear on television and elsewhere as dark-bearded men who harbour medieval beliefs that involve terms such as jihad and sharia. Plenty of demeaning epithets spring to mind when describing such militants, but revolutionary is not really one of them.

But what could be more revolutionary than indiscriminate militarism? Terrorists use undiscerning violence to political ends. So-called Islamic State and al Qaeda, two of 21st-century terrorism’s most notable names, peddle narratives that are...