Sentence:  Now let us <WSD>imagine</WSD> a wing of B-52 's , on alert near their `` positive control ( or fail-safe ) points '' , the spots on the map , many miles from Soviet territory , beyond which they are forbidden to fly without specific orders to proceed to their targets . 
Meaning of the word marked with <WSD> tags:  form a mental image of something that is not present or that is not the case