This is more of a personal view...

Well , many countries detain , prevent and stop possible terrorist activites across the globe , but the thing is , these are little more than short-term measures.

Even if we cut off their heads ( Their leaders ) , even if we place their organisation in shambles , we seem to have forgotten that what keeps these people together is the idea in itself.

These people would always be there as long as the idea itself exists. An idea that converts the views of the people. The true enemy isn't these known leaders of the terrorist in question , the true enemy is the idea itself.
Terrorism will continue if the "idea" was passed on , to put it simply , the idea is what these people worships and the people are the agents to act out it's will for they believe in it.

If we can not stem the flow of this "belief" that they burn deep in their hearts , we can not permanently end terrorism , we can stall it , we can keep the people safe from it , but we can not it away since it is something that is passed on from people to people.
So , how exactly do we end this War in question if we do not even have the means to defeat this enemy in question?

It is like fighting against a hydra , when one head is destroyed , another takes it's place , the only means to end it is to stem it from the root.