WASHINGTON, D.C., May 22, 1863.

Maj. Gen. John M. Schofield, St. Louis, Mo.

General—You have been ordered, by the direction of the President, to relieve Maj. Gen. S. R. Curtis from the command of the Department of the Missouri. This is one of the most important military departments in the United States, and the command will require the exercise of military talent as well as administrative ability, and the utmost vigilance. Your acquaintance with the country and the leading men of your department will be of great value to you in the performance of the arduous and important duties of your command.

It is not intended to embarrass you with minute and detailed instructions. The correspondence between these headquarters and Major-General Curtis will put you in possession of the general views of the Government in regard to military operations. I will state them briefly.

General Curtis' Pea Ridge campaign was simply to expel Price's army from Missouri; that was not deemed a proper line by which to invade Arkansas. Hence he was directed to unite with Steele and move down White River. As soon as the Mississippi was opened to the Arkansas, the former became the true base and the latter the true line of operations. I endeavored to impress this upon General Curtis. But he brought troops from Helena to operate from Pilot Knob, and again pushed forward a column into Western Arkansas. If, on the contrary, he had simply held two or three fortified points, like Springfield, Rolla, and Pilot Knob, and pushed his entire force from the Mississippi River to Little Rock, I think Missouri would have been freed from all fear of invasion and the enemy kept south of the Arkansas River.

Again, my dispatches to General Curtis will show that I have frequently urged upon him not to scatter his troops so much in the interior of the department, but to push them forward for the defense of the southern frontier, and send all who could be spared for such purpose down the Mississippi or to General Rosecrans; but it seems that the general has been under a serious apprehension of insurrections in the interior and northern counties. From the best advices we could obtain here, there were not sufficient grounds for such apprehensions. But, as General Curtis had better means of judging of the dangers, I did not deem it proper to entirely disregard his fears. In the early part of the war, when Price was within the State, or near the frontier, with a large army, there was a necessity for a considerable force in the interior, but the case is now very different, and I am told by reliable Union men that the volunteer troops, especially those from Kansas, in the counties on the Missouri River, do much more harm than good by annoying, irritating, and plundering the inhabitants. It is said that those there who at the outset sided with Price and his rebel gang, but have since been permitted to return and settle down as quiet and peaceable citizens, are now treated as enemies. No worse policy could possibly be adopted. It is hoped you will remedy these alleged evils, and send south into the field all the volunteer troops who can be spared from Missouri and Kansas. There has been no hostile force in Kansas since the beginning of this war, nor has there been, so far as I could learn, any danger of an invasion of that State, or of an insurrection of its inhabitants against the Government and authority of the United States; and yet a very large force has been kept and supported there, at an enormous expense to the National Treasury, and to the annoyance and injury of the inhabitants of the bordering territory. Both while in command of that department and since, I have endeavored to bring these forces into the field, where they could be made useful to the Government; but in these efforts I have been overruled, and, for reasons which I could never fully understand, these enormously expensive troops have been left in Kansas, where they were of no possible use, or sent into Missouri, where they were very much worse than useless. In my opinion, they should be either sent to Salt Lake, to guard the emigrant trains, or moved south to fight the rebels. In whatever use you may determine to make of these troops, you will have all the support which the War Department and these headquarters can give you. A regiment of Nebraska cavalry, on report of General Curtis that it could be spared from his department, was ordered some time ago to report for duty to General Pope, at Sioux City, for operations against the Indians. The authorities of Nebraska afterward protested against this order, and General Curtis asked that it be rescinded. This was refused. Nevertheless, General Pope reports that the order has never been complied with, and I cannot ascertain from General Curtis how the matter now really stands. You will immediately examine into this matter, and either carry out the original order to General Curtis, or use these troops to escort emigrant trains to Salt Lake, as under existing circumstances you may deem best. You will, as soon as you ascertain the real facts of the case, advise General Pope, and give him all possible assistance in his contemplated Indian campaign. At this distance, and acting under very imperfect information, I cannot give you on these subjects very positive or minute instructions. Much must be left to your discretion and more enlightened judgment; but we will leave, for the present, active military operations in the field, and direct our attention for a moment to administrative matter, which will constitute the most annoying, arduous, perplexing, and responsible duties of your command.

On this subject I commend to your careful attention the field instructions published in General Orders, No. 100, current series. These instructions have been most carefully considered before publication. Nevertheless, they are very imperfect, and as Missouri is peculiarly situated, many questions may arise which are not here alluded to. I can only advise you, in regard to such matters, to consult the best authorities, and to act with deliberation and [coolness?] upon each separate question as it arises. A hasty and inconsiderate decision often leads to serious difficulties and embarrassment. On such matters I will give you all the assistance which time and opportunity will permit. In referring these questions to these headquarters, you will take into consideration that I have very little time to devote to a single military department, and more particularly to an individual case.

In conclusion, general, I desire to assure you that in the high and responsible position and duties to which you are assigned you will have all the support, assistance, and co-operation which can be given you from these headquarters. You owe your present appointment entirely to the choice of the President himself. I have not, directly or indirectly, interfered in the matter; but I fully concur in the choice, and will give you all possible support and assistance in the performance of the arduous duties imposed upon you.

You have just left General Rosecrans, and know his want of cavalry. If you can assist him in this matter, I desire you will do so without delay. If you can raise any troops in Northern Missouri, Kansas, Nebraska, or Colorado to guard emigrant trains, report by telegraph.

Very respectfully, your obedient servant,
H. W. HALLECK,
General-in-Chief.