The enemy is not, of course, a religion - most Muslims deplore what has occurred. Nor is it a single state, though this form of terrorism needs the support of states to give it succour. Perhaps the best parallel is with early communism. Islamic extremism today, like bolshevism in the past, is an armed doctrine. It is an aggressive ideology promoted by fanatical, well-armed devotees. And, like communism, it requires an all-embracing long-term strategy to defeat it.