Sentence:  No <WSD>Smokey Bears</WSD>: You can't shoot something you can't see. The Air Force in Viet Nam has special teams that blast away tree leaves and other shrubbery beside canals that offer hiding places for the Viet Cong. The motto of these defoliation teams: "Only you can prevent forests." 
Meaning of the word marked with <WSD> tags:  (military slang) An aircraft used to drop defoliants in the Viet Nam war.