The distinction between strategy and tactics, not always clearly understood, is in substance drawn thus by General Dufour.  Strategy involves general movements and the general arrangement of campaigns, depending chiefly upon the topographical features of the country which is the scene of operations,—­while tactics relate to the minor details of campaigns, as the disposition for marches and battles, the arrangement of camps, etc.  Strategy depends upon circumstances fixed in their nature, and is the same always and everywhere; but tactics must be modified to suit degree of skill, arms, and manner of fighting of the combatants.  Hence, “much instruction in strategy may be derived from the study of history; but very grave errors will result, if we attempt to apply in the armies of the present day the tactics of the ancients.  This fault has been committed by more than one man of merit, for want of reflection upon the great difference between our missile weapons and those of the ancients, and upon the resulting differences in the arrangement of troops for combat.”  Our own military leaders have not entirely avoided mistakes of this kind in the conduct of the present war.

The treatise before us elucidates the general principles of strategy and tactics, and applies them to the different classes of field—­operations, without entering into details, or describing the minor manoeuvres, which belong more appropriately to another class of works.

The first chapter treats of bases and lines of operations, strategic points, plans of offensive and defensive campaigns, and strategical operations.  Under the last head are embraced forward movements and retreats, diversions, (combined movements and detachments,) the pursuit of a defeated enemy, and the holding of a conquered country.  The great lesson of the chapter, prominent in almost every paragraph, is the necessity of concentration.  Divergent marches, scattering of forces, unless ample facilities are secured for a speedy rally, when necessary, to a common point, are among the most fruitful sources of disaster.

The organization of armies next receives attention.  The explanation of the composition of the army, its divisions and subdivisions, and the adjustment of the relative proportions of the different classes of troops, is brief and lucid.  In the article on the formation of troops the relative merits of formation in two ranks or three are discussed at length.

Under the head of marches and manoeuvres are considered the rules by which these movements should be conducted.  These apply to the adjustment of the columns, and the division, when necessary, of the forces upon different roads in order to facilitate progress and make subsistence more easy, the detailing of scouts and advance and rear guards, etc.  The adaptation of these rules to forward movements and battles leads to a description of the order of march of the division, the precautions to be observed in the passage of defiles,