Sentence:  It seems reasonable that if general nuclear war is not to <WSD>be</WSD> one cataclysmic act of burning each other 's citizens to cinders , we must have a manned strategic force of long-endurance aircraft capable of going into China or Russia to find and destroy their strategic forces which continued to threaten us . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)