Sentence:  Political interference in Africa and Asia and even in Latin America ( though limited in Latin America by the special interest of the United States as expressed in the Monroe Doctrine , itself from the outset related to European politics and long dependent upon the `` balance of power '' system in Europe ) <WSD>was</WSD> necessary in order to preserve both common economic values and the European `` balance '' itself . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)