Sentence:  In a book review of `` The Soviet Cultural Offensive '' , he says , `` Long before the State Department organized its bureaucracy into an East-West Contacts Staff in order to wage a cultural counter-offensive within Soviet borders , the sharp <WSD>cutting-edge</WSD> of American culture had carved its mark across the Russian steppes , as when the enterprising promoters of ' Porgy and Bess ' overrode the State Department to carry the contemporary ' cultural warfare ' behind the enemy lines . 
Meaning of the word marked with <WSD> tags:  the position of greatest importance or advancement; the leading position in any movement or field