On the 23rd of July, 1862, Major-General H. W. Halleck arrived at Washington, whither he had been summoned from the west, to assume the chief command of all the armies of the United States. It was felt by the government that there ought now to be a military head of affairs. McClellan was still on the James river. On assuming command, General Halleck visited General McClellan at Harrison’s Landing, and took counsel with him, as to future movements. But the respective plans of the two generals did not coincide; and, of course, the policy of General Halleck prevailed. McClellan wished for reinforcements, and desired once more to advance against Richmond, by way of the Peninsula. General Halleck, however, ordered him to evacuate the Peninsula, and join his forces to those of the Army of Virginia. The latter had, meantime, been formed, by the consolidation of the forces under Banks, McDowell, and Fremont, its command being intrusted to General Pope. This officer took the field on the 27th of July, being charged to protect the city of Washington, guard the valley of the Shenandoah against further rebel raids, and, by bold advances against Richmond from the north, to distract the attention of the foe from the projected movement of McClellan’s forces, from Harrison’s Landing to Acquia Creek. The Army of Virginia consisted, at this time, of twenty-eight thousand men, and was stationed in the vicinity of Culpepper and Fredericksburg, on the northern bank of the Rapidan river. It was the 7th of August when General Pope learned that the rebels were crossing the Rapidan, in great force. Those of his troops which had been dispersed for the sake of observation, received orders to rally immediately at Culpepper. Crawford’s brigade of Banks’s corps was, during the forenoon of the next day, dispatched towards Cedar Mountain, in order that it might, so far as possible, retard the movements of the enemy. General Banks, on the evening of the 8th, had arrived from Hazel river; and early on Saturday morning he was sent forward with his corps of seven thousand men to join General Crawford. The rebels had already, on Thursday, the 7th of August, stationed themselves on an eminence near Culpepper Court House, called Cedar Mountain; having crossed the Rapidan under command of General Stonewall Jackson. General Sigel, by forced marches, was hastening to the support of General Banks.