Sentence:  Since the strength of the Mexicans had been underrated , too small a posse had been collected , and since the deputy had not been provided with search warrants , MacPherson and his men decided it <WSD>was</WSD> much wiser to withdraw . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)