Having given his general instructions, the flag officer could intrust the details of preparation to his subordinates; but no one could relieve him of the momentous decision upon which the issues of the campaign must turn. The responsibility of rejecting one course of action and adopting another was his alone; and as has already been remarked, the wording of the department's order, literally understood, imposed upon him the task of reducing the forts before approaching the city. The questions involved were essentially the same as those presented to every general officer when the course of a campaign has brought him face to face with a strong position of the enemy. Shall it be carried by direct attack, and, until so subdued, arrest the progress of the army? or can it be rendered impotent or untenable by severing its communications and by operations directed against the district in its rear, which it protects, and upon which it also depends? The direct attack may be by assault, by investment, or by regular siege approaches; but whatever the method, the result is the same--the assailant is detained for a longer or shorter time before the position. During such detention the post fulfills its mission of securing the region it covers, and permits there the uninterrupted prosecution of the military efforts of every character which are designed to impede the progress of the invader. To such cases no general rule applies; each turns upon particular conditions, and, although close similarities may exist between various instances, probably no two are entirely identical. It is evident, however, that very much will depend upon the offensive power shut up in the position under consideration. If it be great walled town, such as are found on the Continent of Europe, behind whose defenses are sheltered numerous troops, the assailant who advances beyond it thereby exposes his communications to attack; and, to guard against this danger, must protect them by a force adequate to hold the garrison in check. If, again, there be but a single line by which the communications can be maintained, by which supplies and re-enforcements can go forward, and that line passes close under the work and is commanded by it, the garrison may be small, incapable of external action, and yet may vitally affect the future operations of the venturesome enemy who dares to leave it unsubdued behind him. Such, to some extent, was the Fort of Bard, in the narrow pass of the Dora Baltea, to Napoleon's crossing of the St. Bernard in 1800; and such, to some extent, would be Forts Jackson and St. Philip to Farragut's fleet after it had fought its way above. The Mississippi was the great line of communication for the fleet; no other was comparable to it--except as a by-path in a mountain is comparable to a royal highway--and the forts commanded the Mississippi. Their own offensive power was limited to the range of their guns; their garrisons