Sentence:  Such problems are of extreme interest as well as importance and are so much like fighting in a rain forest or guerrilla warfare at night in tall <WSD>grass</WSD> that we might have to re-examine primitive conflicts for what they could teach . 
Meaning of the word marked with <WSD> tags:  narrow-leaved green herbage: grown as lawns; used as pasture for grazing animals; cut and dried as hay