der 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.

The weak point of McClellan's strategy was making itself felt. In
advancing on Richmond by way of the Peninsula he had deliberately
adopted what are called in strategy "the exterior lines." That is,
his forces were distributed on the arc of a circle, of which Richmond
and the Confederate army were the centre. If, landing on the
Peni