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 <WSD>ruling</WSD> world finance , was 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:  exercise authority over; as of nations