To satisfy himself more fully about the actual situation, the President made a visit to Harrison’s Landing on July 8 and 9, and held personal interviews with McClellan and his leading generals.  While the question of removing the army underwent considerable discussion, the President left it undecided for the present; but on July 11, soon after his return to Washington, he issued an order: 

“That Major-General Henry W. Halleck be assigned to command the whole land forces of the United States, as general-in-chief, and that he repair to this capital so soon as he can with safety to the positions and operations within the department now under his charge.”

Though General Halleck was loath to leave his command in the West, he made the necessary dispositions there, and in obedience to the President’s order reached Washington on July 23, and assumed command of all the armies as general-in-chief.  On the day following he proceeded to General McClellan’s headquarters at Harrison’s Landing, and after two days’ consultation reached the same conclusion at which the President had already arrived, that the Army of the Potomac must be withdrawn.  McClellan strongly objected to this course.  He wished to be reinforced so that he might resume his operations against Richmond.  To do this he wanted fifty thousand more men, which number it was impossible to give him, as he had already been pointedly informed by the President.  On Halleck’s return to Washington, it was, on further consultation, resolved to bring the Army of the Potomac back to Acquia Creek and unite it with the army of Pope.

On July 30, McClellan received a preliminary order to send away his sick, and the withdrawal of his entire force was ordered by telegraph on August 3.  With the obstinacy and persistence that characterized his course from first to last, McClellan still protested against the change, and when Halleck in a calm letter answered his objections with both the advantages and the necessity of the order, McClellan’s movement of withdrawal was so delayed that fully eleven days of inestimable time were unnecessarily lost, and the army of Pope was thereby put in serious peril.

Meanwhile, under President Lincoln’s order of June 26, General Pope had left the West, and about the first of July reached Washington, where for two weeks, in consultation with the President and the Secretary of War, he studied the military situation, and on July 14 assumed command of the Army of Virginia, consisting of the corps of General Fremont, eleven thousand five hundred strong, and that of General Banks, eight thousand strong, in the Shenandoah valley, and the corps of General McDowell, eighteen thousand five hundred strong, with one division at Manassas and the other at Fredericksburg.  It is unnecessary to relate in detail the campaign which followed.  Pope intelligently and faithfully performed the task imposed on him to concentrate his forces and hold in check the advance of the enemy, which began as soon as the Confederates learned of the evacuation of Harrison’s Landing.