Sentence:  Thus , to cite but one example , the Pax Britannica of the nineteenth century , whether with the British navy ruling the seas or with the City of London ruling world finance , <WSD>was</WSD> strictly national in motivation , however much other nations ( e. g. , the United States ) may have incidentally benefited . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)