LETTERS OF INSTRUCTION
Letters of Instruction chiefly differ from orders, operation orders, and field orders in their lack of definition of specific tactical duties. They are truly instructions. They deal mainly with strategic considerations and general plans, because the writer is usually far away from, or not in direct command of, the units which are going to carry out the general plans.
At the beginning of campaigns letters of instruction enumerate the troops of the various commands and the corresponding leaders.
“In armies, combat orders will often be in the form of, or a part of, letters of instruction to the commanding generals in the field armies composing the army. But where the field armies are within supporting distance of each other and can mutually coöperate in the task assigned them, formal combat orders may be issued. Such orders are necessarily general in character and consist of a statement of the objective sought by the army commander, and of the part he expects each field army to play in attaining this objective. The army commander, either by means of letters of instruction or by personal conferences with his field army commanders, fully acquaints them not only with the immediate end in view, but also with so much of his future plans as may be necessary to insure thorough cooperation on their part.”[17]
In the illustration which follows, President Lincoln outlines a general offensive to the various armies. As commander-in-chief he issues the substance of a letter of instructions in the form of an executive order. In it we shall notice that he does not prescribe any specific movement of troops.
Executive Mansion, Washington, Jan. 27, 1862.
President’s General War Order, No. 1.
Ordered: That the 22d day of February, 1862, be the day for a general movement of the land and naval forces of the United States against the insurgent forces.
That, especially,
The army at and about Fortress Monroe,
The army of the Potomac,
The army of West Virginia,
The army near Mumfordsville, Kentucky,
The army and flotilla at Cairo,
And a naval force in the Gulf of Mexico, be ready to move on that day.
That all other forces, both land and naval, with their respective commanders, obey existing orders for the time, and be ready to obey additional orders when duly given.
That the heads of departments, and especially the Secretaries of War and of the Navy, with all their subordinates, and the General-in-Chief, with all other commanders and subordinates of land and naval forces, will severally be held to their strict and full responsibilities for prompt execution of this order.
ABRAHAM LINCOLN.
The following is a more usual form of letter of instructions. This time it goes directly from the commander-in-chief to the general-in-chief:
May 24, 1862.
From Washington, 24th.
Maj.-Gen. G. B. McClellan,—
I left General McDowell’s camp at dark last evening. Shield’s command is there, but it is so worn that he cannot move before Monday morning, the twenty-sixth (26th). We have so thinned our line to get troops for other places, that it was broken yesterday at Front Royal, with a probable loss to us of one (1) regiment infantry, two (2) companies cavalry, putting General Banks in some peril.
The enemy’s forces under General Anderson, now opposing General McDowell’s advance, have as their line of supply and retreat the road to Richmond.
If, in conjunction with McDowell’s movement against Anderson, you could send a force from your right to cut off the enemy’s supplies from Richmond, preserve the railroad bridges across the two (2) forks of the Pamunkey, and intercept the enemy’s retreat, you will prevent the army now opposed to you from receiving an accession of numbers of nearly fifteen thousand (15,000) men, and if you succeed in saving the bridges, you will secure a line of railroad for supplies in addition to the one you now have. Can you not do this almost as well as not, while you are building the Chickahominy bridges? McDowell and Shields both say you can, and positively will, move Monday morning. I wish you to march cautiously and safely.
You will have command of McDowell after he joins you, precisely as you indicated in your long dispatch to us of the twenty-first (21st).
A. LINCOLN,
President.
As you see, the above example does no more than suggest to General McClellan from a strategic standpoint certain courses open to him. The general-in-chief on the spot is the one to make the decision.
To progress in our examples, let us take one issued by the general-in-chief to one of his subordinate generals.
Headquarters of the Army,
Washington, Feb. 23, 1862.
Maj.-Gen. B. F. Butler,
U. S. Volunteers,—
General:—You are assigned to the command of the land forces destined to coöperate with the navy, in the attack upon New Orleans. You will use every means to keep your destination a profound secret, even from your staff officers, with the exception of your chief-of-staff, and Lieut. Weitzel, of the engineers. The force at your disposal will consist of the first 13 regiments named in your memorandum handed to me in person, the 21st Indiana, 4th Wisconsin, and 6th Michigan (old and good regiments from Baltimore).
The 21st Indiana, 4th Wisconsin, and the 6th Michigan, will await your orders at Fort Monroe.
Two companies of the 21st Indiana, are well-drilled as heavy artillery. The cavalry force already en route for Ship Island, will be sufficient for your purposes.
After full consultation with officers well acquainted with the country in which it is proposed to operate, I have arrived at the conclusion that (2) two light batteries fully equipped and (1) one without horses, will be all that are necessary.
This will make your force about 14,400 infantry, 275 cavalry, 680 artillery; total 15,255 men.
The commanding general of the Department of Key West, is authorized to loan you, temporarily, 2 regiments; Fort Pickens can probably give you another, which will bring your force to nearly 18,000.
The object of your expedition is one of vital importance, the capture of New Orleans. The route selected is up the Mississippi River, and the first obstacle to be encountered (perhaps the only one) is in the resistance of Forts St. Philip and Jackson. It is expected that the navy can reduce these works; in that case, you will, after their capture, leave a sufficient garrison in them to render them perfectly secure; and it is recommended, that on the upward passage, a few heavy guns, and some troops, be left at Pilot Station (at the forks of the river), to cover a retreat in the event of disaster. These troops and guns, will, of course, be removed as soon as the forts are captured.
Should the navy fail to reduce the works, you will land your forces and siege train, and endeavor to breach the works, silence their fire, and carry them by assault.
The next resistance will be near the English Bend, where there are some earthen batteries; here it may be necessary for you to land your troops and coöperate with the naval attack, although it is more than probable, that the navy, unassisted, can accomplish the result. If these works are taken, the city of New Orleans necessarily falls. In that event, it will probably be best to occupy Algiers with the mass of your troops, also, the eastern bank of the river above the city; it may be necessary to place some troops in the city to preserve order, but if there appears sufficient Union sentiment to control the city, it may be best for purposes of discipline to keep your men out of the city.
After obtaining possession of New Orleans, it will be necessary to reduce all the works guarding its approaches from the east, and particularly to gain the Manchac Pass. Baton Rouge, Berwick Bay, and Fort Livingston will next claim your attention.
A feint at Galveston may facilitate the objects we have in view. I need not call your attention to the necessity of gaining possession of all the rolling stock you can on the different railways, and of obtaining control of the roads themselves. The occupation of Baton Rouge by a combined naval and land force, should be accomplished as soon as possible after you have gained New Orleans. Then endeavor to open your communication with the northern column by the Mississippi, always bearing in mind the necessity of occupying Jackson, Mississippi, as soon as you can safely do so, either after, or before you have effected the junction. Allow nothing to divert you from obtaining possession of all the approaches to New Orleans. When that object is accomplished to its fullest extent, it will be necessary to make a combined attack on Mobile, in order to gain possession of the harbor and works, as well as to control the railway terminus at the city.
In regard to this, I will send more detailed instructions as the operations of the northern column develop themselves.
I may briefly state that the general objects of the expedition are: First, The reduction of New Orleans and all its approaches: then Mobile and its defenses: then Pensacola, Galveston, etc. It is probable that by the time New Orleans has been reduced it will be in the power of the government to reinforce the land forces sufficiently to accomplish all these objects; in the meantime you will please give all the assistance in your power to the army and navy commanders in your vicinity, never losing sight of the fact, that the great object to be achieved is the capture and firm retention of New Orleans.
I am, etc.,
GEO. B. McCLELLAN,
Maj.-Gen. Com’g U. S. A.
General McClellan goes more into detail than does the President. He is considering the situation on more technical lines. Yet he does not go beyond the limits of strategy in outlining the general plan. He still conforms to the principles of letters of instruction. If we were to follow General Butler in his journey to the Gulf, we should perceive in his orders the disappearance of the strategic and the appearance of the tactical idea. Later we should discover one of his brigade commanders actually issuing a field order.
Notice in the last example how, on account of its length, General McClellan has made a neat summary of the whole. Notice that in all of these letters the writers have adhered to the principles of rhetoric; and that they have given to the recipient a unified and coherent production. Why? Because the will of the commander is transmitted more quickly in that way.
We have now completed the consideration of the expression which directly affects troops in the field. We have written the field message which brings information to commanders and which helps them to make an estimate of a situation. We have framed the field order which grows out of that estimate and which transforms the decision into action. We have viewed the operation order which is no more than a field order made to fit trench warfare. We have seen orders which are issued in connection with combat so as to govern the movement of trains. We have read letters of instruction which are written by higher commanders in order to regulate in a general way extensive movements. All of these communications bear specifically upon the effort of troops toward success in battle—the ultimate object of all military training.
In leaving this most important part of our professional work, we might take with us this one idea. We can best express ourselves in any of the communications we have studied by having all the thoughts of one kind together and the different kinds in an orderly arrangement. Whenever it is possible we should keep the paragraph sequence,
(a) Enemy.
(b) Own troops.
(c) Plan.
CHAPTER XI
THE WAR DIARY—THE REPORT—ROUTINE ORDERS
We have heretofore considered those communications which aid combat. We now take up those which have no direct bearing upon the outcome of an engagement. We have seen how the field message makes possible by its fresh information the plan for battle, how the field and operation orders frame that plan for battle, how the order maneuvers the trains in connection with battle, and how letters of instruction issue general directions for a campaign of many battles. We now come to the place where the maneuver, enterprise, or undertaking is over. For a variety of future benefits we must have a record of those occurrences. The War Diary and The Report are the communications which perform that office.