There were several circumstances combined, in the situation in which Alexander was placed, to afford him a great opportunity for the exercise of his vast powers. His native country was on the confines of Europe and Asia. Now Europe and Asia were, in those days, as now, marked and distinguished by two vast masses of social and civilized life, widely dissimilar from each other. The Asiatic side was occupied by the Persians, the Medes, and the Assyrians. The European side by the Greeks and Romans. They were separated from each other by the waters of the Hellespont, the Ægean Sea, and the Mediterranean, as will be seen by the map. These waters constituted a sort of natural barrier, which kept the two races apart. The races formed, accordingly, two vast organizations, distinct and widely different from each other, and of course rivals and enemies.