It is time now to return to the theatre of war in Virginia, where, it will be remembered, we left the Confederate forces in the act of rapidly withdrawing southward from the line of intrenchments which they had so long held at Manassas.  This unexpected backward movement upon their part deprived the Urbana route, which McClellan had hitherto so strenuously advocated, of its chief strategic advantages, and therefore reopened the old question which had been discussed between him and Mr. Lincoln.  To the civilian mind a movement after the retreating enemy along the direct line to Richmond, now more than ever before, seemed the natural scheme.  But to this McClellan still remained unalterably opposed.  In the letter of February 3 he had said:  “The worst coming to the worst, we can take Fort Monroe as a base and operate with complete security, although with less celerity and brilliancy of results, up the Peninsula.”  This route, low as he had then placed it in order of desirability, he now adopted as the best resource, or rather as the only measure; and his judgment was ratified upon March 13 by unanimous approval on the part of his four corps commanders.  They however made their approval dependent upon conditions, among which were:  that, before beginning the advance along this line, the new rebel ram Merrimac (or Virginia), just finished at Norfolk on the James River, should be neutralized, and that a naval auxiliary force should silence, or be ready to aid in silencing, the rebel batteries on the York River.  In fact, and very unfortunately, the former of these conditions was not fulfilled until the time of its usefulness for this specific purpose was over, and the latter condition was entirely neglected.  It was also distinctly stipulated that “the force to be left to cover Washington shall be such as to give an entire feeling of security for its safety from menace.”  Keyes, Heintzelman and McDowell conceived “that, with the forts on the right bank of the Potomac fully garrisoned, and those on the left bank occupied, a covering force, in front of the Virginia line, of 25,000 men would suffice.”  Sumner said:  “A total of 40,000 for the defense of the city would suffice."[4] On the same day Stanton informed McClellan that the President “made no objection” to this plan, but directed that a sufficient force should be left to hold Manassas Junction and to make Washington “entirely secure.”  The closing sentence was:  “At all events, move ... at once in pursuit of the enemy by some route.”  Thus at last two important facts were established:  that the route up the Peninsula should be tried; and that the patience of the administration was exhausted.