“I am instructed to telegraph you as follows:  The President directs that you cross the Potomac and give battle to the enemy, or drive him south.  Your army must move now while the roads are good.  If you cross the river between the enemy and Washington, and cover the latter by your operation, you can be reinforced with thirty thousand men.  If you move up the valley of the Shenandoah, not more than twelve thousand or fifteen thousand can be sent to you.  The President advises the interior line, between Washington and the enemy, but does not order it.  He is very desirous that your army move as soon as possible.  You will immediately report what line you adopt, and when you intend to cross the river; also to what point the reinforcements are to be sent.  It is necessary that the plan of your operations be positively determined on before orders are given for building bridges and repairing railroads.  I am directed to add that the Secretary of War and the general-in-chief fully concur with the President in these instructions.”

This express order was reinforced by a long letter from the President, dated October 13, specifically pointing out the decided advantages McClellan possessed over the enemy, and suggesting a plan of campaign even to details, the importance and value of which was self-evident.

“You remember my speaking to you of what I called your over-cautiousness.  Are you not over-cautious when you assume that you cannot do what the enemy is constantly doing?  Should you not claim to be at least his equal in prowess, and act upon the claim?...  Change positions with the enemy, and think you not he would break your communication with Richmond within the next twenty-four hours?  You dread his going into Pennsylvania, but if he does so in full force, he gives up his communications to you absolutely, and you have nothing to do but to follow and ruin him.  If he does so with less than full force, fall upon and beat what is left behind all the easier.  Exclusive of the water-line, you are now nearer Richmond than the enemy is by the route that you can and he must take.  Why can you not reach there before him, unless you admit that he is more than your equal on a march?  His route is the arc of a circle, while yours is the chord.  The roads are as good on yours as on his.  You know I desired, but did not order, you to cross the Potomac below instead of above the Shenandoah and Blue Ridge.  My idea was that this would at once menace the enemy’s communications, which I would seize, if he would permit.  If he should move northward I would follow him closely, holding his communications.  If he should prevent our seizing his communications and move toward Richmond, I would press closely to him, fight him, if a favorable opportunity should present, and at least try to beat him to Richmond on the inside track.  I say ‘try’; if we never try we shall never succeed.  If he makes a stand at Winchester, moving neither north nor south, I would fight him there, on the idea that if we cannot beat him when he bears the wastage of coming to us, we never can when we bear the wastage of going to him.”