Temporary lines of defence are such as are taken up merely for the campaign. Napoleon's position in Saxony, in 1813; the line of the allies in Belgium, in 1815; the line of the Marne, in 1814, are examples of temporary lines of defence. It will be seen from these remarks that lines of defence are not necessarily bases of operation. _Strategic positions_ are such as are taken up during the operations of a war, either by a _corps d'armee_ or grand detachment, for the purpose of checking or observing an opposing force; they are named thus to distinguish them from tactical positions or fields of battle. The positions of Napoleon at Rivoli, Verona, and Legnano, in 1796 and 1797, to watch the Adige; his positions on the Passarge, in 1807, and in Saxony and Silesia in front of his line of defence, in 1813; and Massena's positions on the Albis, along the Limmat and the Aar, in 1799, are examples under this head. Before proceeding further it may be well to illustrate the strategic relations of lines and positions by the use of diagrams. (Fig. 1.) The army at A covers the whole of the ground in rear of the line DC perpendicular to the line AB, the position of the enemy being at B. (Fig. 2.) AJ being equal to BJ, A will still cover every thing in rear of DC. (Fig. 3.) If the army A is obliged to cover the point _a_, the army B will cover all the space without the circle whose radius is _a_ B; and of course A continues to cover the point _a_ so long as it remains within this circle _a_ B. _A line of operations_ embraces that portion of the theatre of war which an army or _corps d'armee_ passes over in attaining its object; _the front of operations_ is the front formed by the army as it advances on this line. When an army acts as a single mass, without forming independent corps, the line it follows is denominated a _simple line of operations_. If two or more corps act in an isolated manner, but against the same opposing force, they are said to follow _double_ or _multiple lines_. The lines by which Moreau and Jourdan entered Germany in 1796, were double lines; but Napoleon's advance by Bamberg and Gera, in 1806, although moving in seven distinct _corps d'armee,_ formed but a single line of operations. _Interior lines of operations_ are those followed by an army which operates between the enemy's lines in such a way as to be able to concentrate his forces on one of these lines before the other can be brought to its assistance. For example, Napoleon's line of operations in 1814, between the Marne and the Seine, where he manoeuvred with so much skill and success against the immensely superior forces of the allies.