When Rosecrans's letter, enclosing his final plan, reached Washington, McClellan had taken the field, and President Lincoln had made use of the occasion to relieve him from the direction of all other forces, so that he might give undivided attention to his campaign with the Potomac army. This was done by an executive order on March 11, [Footnote: Official Records, vol. v. p. 54.] which assigned General Halleck to the command of everything west of a line drawn north and south through Knoxville, Tennessee, and formed the Mountain Department from the territory between Halleck and McClellan. This last department was put under the command of Major-General John C. Fremont. General Banks was commanding in the Shenandoah valley, but he was at this time subordinate to McClellan. These changes were unexpected to both McClellan and Rosecrans. The change in McClellan's relations to the whole army was the natural result of his inactivity during the autumn of 1861, and the consequent loss of confidence in him. The union of Buell's and Halleck's commands in the west was the natural counterpart to the concentration of Confederate armies under A. S. Johnston at Corinth, Miss., and was a step in the right direction. There was, however, a little too much sentiment and too little practical war in the construction of the Mountain Department out of five hundred miles of mountain ranges, and the appointment of the "path-finder" to command it was consistent with the romantic character of the whole. The mountains formed a natural and admirable barrier, at which comparatively small bodies of troops could cover and protect the Ohio valley behind them; but, for reasons which I have already pointed out, extensive military operations across and beyond the Alleghanies from west or east were impracticable, because a wilderness a hundred miles wide, crossed by few and most difficult roads, rendered it impossible to supply troops from depots on either side. Such assurances of other satisfactory employment seem to have been given Rosecrans that he acquiesced without open complaint, and prepared to turn over his command to Fremont when the latter should arrive in West Virginia. Political motives had, no doubt, much to do with Fremont's appointment. The President had lost faith in his military capacity as well as in his administrative ability, but the party which elected Mr. Lincoln had not. The Republicans of the Northern States had a warm side for the man they had nominated for the Presidency in 1856, and there was a general feeling among them that Fremont should have at least another opportunity to show what he could do in the field. I myself shared that feeling, and reported to him as my immediate superior with earnest cordiality. [Footnote: Official Records, vol. xii. pt. iii. p. 35.]