南北問題
Further dividing the map by geographic features, Mahan stated that the two most influential lines of division would be the Suez Canal and Panama Canal. As most developed nations and resources lay above the North–South divide, politics and commerce north of the two canals would be of much greater importance than those occurring south of the canals. As such, the great progress of historical development would not flow from north to south, but from east to west, in this case leading toward Asia as the locus of advance.