Of what significance is the setting in "The Destructors"?

London has been "blitzed" during WWII, meaning that it has been bombed and torn down by the events of war.  The boys are tearing down their own barriers.  They have rejected the leadership of adults and have established their own heirarchy.  They have taken control of the empty lot and plan to make an incursion into Mr. Thomas' house, just as the Germans were trying to make an incursion into England.  Greene is mimicking the events of the war in a smaller setting, and uses London to reinforce that analogy.