A French army carrying on military operations against Germany would make the Rhine its first base; but if driven from this it would form a second base on the Meuse or Moselle, a third on the Seine, and a fourth on the Loire; or, when driven from the first base, it would take others perpendicular to the front of defence, either to the right, on Befort and Besancon, or to the left, on Mezieres and Sedan. If acting offensively against Prussia and Russia, the Rhine and the Main would form the first base the Elbe and the Oder the second, the Vistula the third, the Nieman the fourth, and the Dwina and the Dnieper the fifth. A French army operating against Spain would have the Pyrenees for its first base; the line of the Ebro for a second, resting its wings on the gulf of Gascony and the Mediterranean. If from this position it advance its left, possessing itself of the kingdom of Valencia, the line of the Sierra d'Estellas becomes its third base of operations against the centre of Spain. A base may be parallel, oblique, or perpendicular to our line of operations, or to the enemy's line of defence. Some prefer one plan and some another; the best authorities, however, think the oblique or perpendicular more advantageous than the parallel; but we are not often at liberty to choose between these, for other considerations usually determine the selection. In 1806, the French forces first moved perpendicular to their base on the Main, but afterwards effected a change of front, and moved on a line oblique or nearly parallel to this base. They had pursued the same plan of operations in the Seven Years' War. The Russians, in 1812, based perpendicularly on the Oka and the Kalouga, and extended their flank march on Wiozma and Krasnoi; in 1813, the allies, based perpendicularly on Bohemia, succeeded in paralyzing Napoleon's army on the Elbe. An American army moving by Lake Champlain, would be based perpendicular on the great line of communication between Boston and Buffalo; if moving from the New England states on Quebec and Montreal, the line of operations would be oblique; and if moving from the Niagara frontier by Lake Ontario and the St. Lawrence, the line would be nearly parallel both to our base and to the enemy's line of defence--an operation, under the circumstances, exceedingly objectionable. Any point in the theatre of operations which gives to the possessor an advantage over his opponent, is regarded as _strategic_. Their geographical position and political and military character, give them a greater or less influence in directing the campaign. These points are occupied by the defensive army, and attacked by the offensive; if on or near the base, they become the _key_ points for the former, and the _objective_ points for the latter.[3] There are also between these two a greater or less number of strategic points, which have an important though inferior influence upon the result of the war.