It might be argued, however, that with an antagonist so supine as Banks Jackson might have openly marched to Staunton by the most direct route; in fact, that he need never have left the Valley at all.  But, had he taken the road across the Valley, he would have advertised his purpose.  Milroy would have received long warning of his approach, and all chance of effecting a surprise would have been lost.

On April 29, the day on which Jackson began his movement, Richmond was still safe.  The Yorktown lines were intact, held by the 53,000 Confederates under Johnston; but it was very evident that they could not be long maintained.

A large siege train had been brought from Washington, and Johnston had already learned that in a few days one hundred pieces of the heaviest ordnance would open fire on his position.  His own armament was altogether inadequate to cope with such ponderous metal.  His strength was not half his adversary’s, and he had determined to retreat without waiting to have his works demolished.

But the mighty army in his front was not the only danger.  McDowell, with 35,000 men, had already concentrated near Falmouth.  Johnston, in falling back on Richmond, was in danger of being caught between two fires, for to oppose McDowell on the Rappahannock Lee had been unable to assemble more than 12,000 Confederates.

These facts were all known to Jackson.  Whether the march to Mechum’s River was intended by him to have any further effect on the Federals than surprising Milroy, and clearing the way for an attack on Banks, it is impossible to say.  It is indisputable, at the same time, that his sudden disappearance from the Valley disturbed Mr. Stanton.  The Secretary of War had suspected that Jackson’s occupation of Swift Run Gap meant mischief.  McDowell, who had been instructed to cross the Rappahannock, was ordered in consequence to stand fast at Falmouth, and was warned that the enemy, amusing McClellan at Yorktown, might make a sudden dash on either himself or Banks.

A few days later McDowell reported that Jackson had passed Gordonsville.  The news came from deserters, “very intelligent men.”  The next day he was informed that Shields was to be transferred to his command, and that he was to bear in mind his instructions as to the defence of Washington.  Banks had already been ordered back to Strasburg.  Now, a few days previously, Stanton had been talking of co-operation between McClellan and McDowell.  Directly he learned that Jackson was east of the Blue Ridge all thought of combination was abandoned; McDowell was held back; Shields was sent to reinforce him; and the possible danger to Washington overrode all other considerations.