n to do so. The bulk of the garrison, under
Major-General French, was directed to take post as a reserve at
Frederick, when our forces moved forward. The general idea of our
advance was to interpose between the enemy and Philadelphia if he
went north, or between him and Baltimore and Washington in case he
turned back. The orders at night were for Buford's division of
cavalry to take post on the left flank, in the direction of Fairfield;
Gregg's division on the right flank at Westminster; and Kilpatrick's
division in advance of the centre, at Littlestown, the different
corps to be posted between New Windsor and Emmetsburg.

Ewell's corps, as stated, were at Carlisle and York, Lee and
Longstreet's at Chambersburg, and Hill's corps at Fayetteville.

Lee was startled to learn from a countryman who came in on the 28th
that Hooker was at Frederick, and not south of the Potomac, as he
had supposed. He saw at once that his communications with Richmond,
about which he was so solicitous, were greatly endangered, for the
Union army could be formed to interpose between him and Williamsport,
and still keep a safe line of retreat open to Washington. This
might not be so great a misfortune to the enemy as regards food
and forage; for he could probably live on the country for some
time, by making predatory excursions in different directions, but
when it came to obtaining fresh supplies of ammunition, the matter
would become very serious. An army only carries a limited amount
of this into the field and must rely upon frequent convoys to keep
up the supply, which is constantly decreasing from the partial
engagements and skirmishes, so prevalent in a hostile country.

The wisdom of Hooker's policy in desiring to assail the rebel
communications is demonstrated by the fact the Lee immediately
turned back. The head of the serpent faced about as soon as its
tail was trodden upon. He came to the conclusion to prevent an
attack against his rear by threatening Baltimore with his whole
force. This would necessarily cause the Union army to march further
east to confront him, and thus prevent it from operating in heavy
force in the Cumberland Valley. Accordingly on the night of the
28th, Lee sent expresses to all his corps commanders to concentrate
at Gettysburg. If he had known that Meade was about to withdraw
all the troops acting against his line of retreat he would probably
have gone on and taken Harrisburg.

As the new commande