Crook led the way across the Potomac at Harper's Ferry on the evening of the 5th of August, Emory followed the next morning, and Ricketts with the Sixth Corps brought up the rear. Averell with the cavalry, as will be remembered, was still far away, engaged in the long chase after McCausland. Hunter took up his position covering Halltown and proceeded to strengthen it by entrenchments. Crook's left rested on the Shenandoah, Emory extended the line to the turnpike road, and Wright carried it to the Potomac. On the very day Grant left City Point, Early marched north from Bunker Hill, meaning to cover McCausland's retreat and to destroy Hunter, and so, curiously enough, it happened that Early's whole army actually crossed the Potomac into Maryland at Martinsburg and Shepherdstown a few hours before Crook passed over the ford at Harper's Ferry into Virginia; and, still more curiously, while, ten days before, the groundless apprehension of another invasion by Early had thrown the North into a fever and the government into a fright, here was Early actually in Maryland on the battle-field of Antietam without producing so much as a sensation. As soon as Early got the first inkling of what was going on behind him, he tripped briskly back to Martinsburg, and finding Hunter at Halltown resumed his old position at Bunker Hill. Grant had already proposed to unite in a single command the four distinct departments covering the theatre of war on the Shenandoah and on the upper Potomac; as the commander he had first suggested Franklin and afterward Meade. Now, since no action had followed either suggestion, he sent up Sheridan, meaning to place him in command of all the active forces of these four departments, for the purpose of overthrowing Early or expelling him from the Shenandoah. Upon learning this, Hunter, to remove the difficulty, asked to be relieved; and thus, on the 7th of August, Grant gained his wish, and an order was issued by the War Department, creating the Middle Military Division, to include Washington, Virginia, West Virginia, Maryland, Pennsylvania, and part of Ohio, and Sheridan was assigned to the command.