Annual Report of the Secretary of War for 1876, which is House Executive Document 1 for the second session of the Forty-fourth Congress (Serial volume 1742), page 462
Headquarters of the Department of Dakota (In the Field)
Camp at Mouth of Rosebud River, Montana Territory June 22nd, 1876
Colonel: The Brigadier-General Commanding directs that, as soon as your regiment can be made ready for the march, you will proceed up the Rosebud in pursuit of the Indians whose trail was discovered by Major Reno a few days since. It is, impossible to give you any definite instructions in regard to this movement, and were it not impossible to do so the Department Commander places too much confidence in your zeal, energy, and ability to wish to impose upon you precise orders which might hamper your action when nearly in contact with the enemy. He will, however, indicate to you his own views of what your action should be, and he desires that you should conform to them unless you shall see sufficient reason for departing from them. He thinks that you should proceed up the Rosebud until you ascertain definitely the direction in which the trail above spoken of leads. Should it be found (as it appears almost certain that it will be found) to turn towards the Little Bighorn, he thinks that you should still proceed southward, perhaps as far as the headwaters of the Tongue, and then turn toward the Little Horn, feeling constantly, however, to your left, so as to preclude the escape of the Indians passing around your left flank.
The column of Colonel Gibbon is now in motion for the mouth of the Big Horn. As soon as it reaches that point will cross the Yellowstone and move up at least as far as the forks of the Big and Little Horns. Of course its future movements must be controlled by circumstances as they arise, but it is hoped that the Indians, if upon the Little Horn, may be so nearly inclosed by the two columns that their escape will be impossible. The Department Commander desires that on your way up the Rosebud you should thoroughly examine the upper part of Tullock's Creek, and that you should endeavor to send a scout through to Colonel Gibbon's command.
The supply-steamer will be pushed up the Big Horn as far as the forks of the river is found to be navigable for that distance, and the Department Commander, who will accompany the column of Colonel Gibbon, desires you to report to him there not later than the expiration of the time for which your troops are rationed, unless in the mean time you receive further orders.
Very respectfully, Your obedient servant,
E. W. Smith, Captain, 18th Infantry A. A. J. G.
LITTLE BIGHORN CAMPAIGN