These two conceptions, these forms in the use of offensive and defensive, appear so frequently in theory and reality, that the imagination is involuntarily disposed to look upon them as intrinsic forms, necessary to attack and defence, which, however, is not really the case, as the smallest reflection will show. We take the earliest opportunity of examining them, that we may obtain once for all clear ideas respecting them, and that, in proceeding with our consideration of the relations of attack and defence, we may be able to set these conceptions aside altogether, and not have our attention for ever distracted by the appearance of advantage and the reverse which they cast upon things. We treat them here as pure abstractions, extract the conception of them like an essence, and reserve our remarks on the part which it has in actual things for a future time. The defending party, both in tactics and in strategy, is supposed to be waiting in expectation, therefore standing, whilst the assailant is imagined to be in movement, and in movement expressly directed against that standing adversary. It follows from this, necessarily, that turning and enveloping is at the option of the assailant only, that is to say, as long as his movement and the immobility of the defensive continue. This freedom of choice of the mode of attack, whether it shall be convergent or not, according as it shall appear advantageous or otherwise, ought to be reckoned as an advantage to the offensive in general. But this choice is free only in tactics; it is not always allowed in strategy. In the first, the points on which the wings rest are hardly ever absolutely secure; but they are very frequently so in strategy, as when the front to be defended stretches in a straight line from one sea to another, or from one neutral territory to another. In such cases, the attack cannot be made in a convergent form, and the liberty of choice is limited. It is limited in a still more embarrassing manner if the assailant is obliged to operate by converging lines. Russia and France cannot attack Germany in any other way than by converging lines; therefore they cannot attack with their forces united. Now if we assume as granted that the concentric form in the action of forces in the majority of cases is the weaker form, then the advantage which the assailant possesses in the greater freedom of choice may probably be completely outweighed by the disadvantage, in other cases, of being compelled to make use of the weaker form. We proceed to examine more closely the action of these forms, both in tactics and in strategy.