When advancing or retreating in line of battle, the usual skirmish-line constitutes the picket-line, and may have "reserves," but usually the main line of battle constitutes the reserve; and in this connection I will state that the recent innovation introduced into the new infantry tactics by General Upton is admirable, for by it each regiment, brigade, and division deployed, sends forward as "skirmishers" the one man of each set of fours, to cover its own front, and these can be recalled or reenforced at pleasure by the bugle-signal.
For flank-guards and rear-guards, one or more companies should be detached under their own officers, instead of making up the guard by detailing men from the several companies.
For regimental or camp guards, the details should be made according to existing army regulations; and all the guards should be posted early in the evening, so as to afford each sentinel or vedette a chance to study his ground before it becomes too dark.
In like manner as to the staff.

The more intimately it comes into contact with the troops, the more useful and valuable it becomes.
The almost entire separation of the staff from the line, as now practised by us, and hitherto by the French, has proved mischievous, and the great retinues of staff-officers with which some of our earlier generals began the war were simply ridiculous.
I don't believe in a chief of staff at all, and any general commanding an army, corps, or division, that has a staff-officer who professes to know more than his chief, is to be pitied.

Each regiment should have a competent adjutant, quartermaster, and commissary, with two or three medical officers.

Each brigade commander should have the same staff, with the addition of a couple of young aides-de-camp, habitually selected from the subalterns of the brigade, who should be good riders, and intelligent enough to give and explain the orders of their general.
The same staff will answer for a division.

The general in command of a separate army, and of a corps d'armee, should have the same professional assistance, with two or more good engineers, and his adjutant-general should exercise all the functions usually ascribed to a chief of staff, viz., he should possess the ability to comprehend the scope of operations, and to make verbally and in writing all the orders and details necessary to carry into effect the views of his general, as well as to keep the returns and records of events for the information of the next higher authority, and for history.