Transfer now your attention back to the Danube when the scene of war is in that region; as it was in 1796, and also frequently was during the period of which we are now speaking.... You have seen before, that, if there be war between Austria and France, as there so often was, the one who held the Danube had a central position in the region. Holding means possession by military power, which power can be used to the full against the North or against the South—offensive power—far more easily than the South and North can combine against him; because he is nearer to each than either is to the other. (See map.) Should North wish to send a big reinforcement to South, it cannot march across the part of the Danube held, but must march around it above or below; exactly as, in 1640, reinforcements from Spain to the Rhine had, so to say, to march around France. In such a march, on land, the reinforcement making it is necessarily in a long column, because roads do not allow a great many men to walk abreast. The road followed designates in fact the alignment of the reinforcement from day to day; and because its advance continually turns the side to the enemy, around whom it is moving, the enemy’s position is said to flank the movement, constituting a recognized danger. It makes no difference whether the line of march is straight or curved; it is extension upon it that constitutes the danger, because the line itself, being thin, is everywhere weak, liable to an attack in force upon a relatively small part of its whole. Communications are exposed, and the enemy has the interior line.... This is an illustration of the force of Napoleon’s saying, that “War is a business of positions.” All this discussion turns on position; the ordinary, semi-permanent, positions of Center, North, and South; or the succession of positions occupied by the detachment on that line of communications along which it moves. This illustrates the importance of positions in a single instance, but is by no means exhaustive of that importance. Fully to comprehend, it is necessary to study military and naval history; bearing steadily in mind Napoleon’s saying, and the definitions of central position, interior lines, and communications.