:We might as well ask why you systematically engage in personal attacks and fail to assume good faith.  We might also ask why you assume that all edits to this article (aside from yours) were made by Koreans.  Regarding your specific complaint, the current form of the sentence was incorrect.  On the other hand, it is true that Korea was united as a single entity from 935 to 1945.  Korea was not a country from 1910 to 1945, but it was nonetheless united.