f November, and, from lack
of subsistence, being unable to continue demonstrations to prevent my
reinforcement of General Grant, began himself to detach to General
Lee by returning Kershaw's division to Petersburg, as was definitely
ascertained by Torbert in a reconnoissance to Mount Jackson. At this
time General Grant wished me to send him the Sixth Corps, and it was
got ready for the purpose, but when I informed him that Torbert's
reconnoissance had developed the fact that Early still retained four
divisions of infantry and one of cavalry, it was decided, on my
suggestion, to let the Sixth Corps remain till the season should be a
little further advanced, when the inclemency of the weather would
preclude infantry campaigning. These conditions came about early in
December, and by the middle of the month the whole of the Sixth Corps
was at Petersburg; simultaneously with its transfer to that line
Early sending his Second Corps to Lee.

During the entire campaign I had been annoyed by guerrilla bands
under such partisan chiefs as Mosby, White, Gilmore, McNeil, and
others, and this had considerably depleted my line-of-battle
strength, necessitating as it did large, escorts for my
supply-trains. The most redoubtable of these leaders was Mosby, whose
force was made up from the country around Upperville, east of the Blue
Ridge, to which section he always fled for a hiding-place when he
scented danger. I had not directed any special operations against
these partisans while the campaign was active, but as Mosby's men had
lately killed, within my lines, my chief quartermaster, Colonel Tolles,
and Medical Inspector Ohlenchlager, I concluded to devote particular
attention to these "irregulars" during the lull that now occurred; so
on the 28th of November, I directed General Merritt to march to the
Loudoun Valley and operate against Mosby, taking care to clear the
country of forage and subsistence, so as to prevent the guerrillas from
being harbored there in the future their destruction or capture being
well-nigh impossible, on account of their intimate knowledge of the
mountain region. Merritt carried out his instructions with his usual
sagacity and thoroughness, sweeping widely over each side of his
general line of march with flankers, who burned the grain and brought
in large herds of cattle, hogs and sheep, which were issued to the
troops.

While Merritt was engaged in this service the Baltimore and Ohio
railroad once m