G. S. Hillard, Life and Campaigns of George B. McClellan, Major-General , U. S. Army

In the course of the 26th, the rapid movement of events, and especially the cloud of advancing forces on our right, every moment growing darker and more menacing, determined General McClellan to pat into immediate execution that plan of transferring his base of operations to the James River which he had been meditating for some days, and in view of which he had already directed large supplies of forage and provisions to be forwarded. The task was one of no common difficulty. The distance between the points of departure and destination was about seventeen miles. An army of ninety thousand men, including cavalry and artillery, was to be marched this distance; and, what was much more difficult, a boundless procession of four thousand wagons, carrying supplies, must go with it, a large siege-train must be transported, and a herd of twenty-five hundred oxen must be driven. For the wagons, the train, and the cattle there was but one road available: luckily, it was in good condition. But it ran north and south, and between it and Richmond there were several roads going east and west, along which attacks might be expected from an active and vigilant enemy. General McClellan, in short, was attempting one of the most difficult and dangerous enterprises in war,--a flank movement in the face of a superior force. But there was no help for it: it must be done.

Time was now an element of the greatest importance.