work of refitting and preparing for offensive operations as soon as
General Sherman should reach us with his troops from West Tennessee.
During this period of activity the enemy committed the serious fault
of detaching Longstreet's corps--sending it to aid in the siege of
Knoxville in East Tennessee--an error which has no justification
whatever, unless it be based on the presumption that it was
absolutely necessary that Longstreet should ultimately rejoin Lee's
army in Virginia by way of Knoxville and Lynchburg, with a chance of
picking up Burnside en route. Thus depleted, Bragg still held
Missionary Ridge in strong force, but that part of his line which
extended across the intervening valley to the northerly point of.
Lookout Mountain was much attenuated.

By the 18th of November General Grant had issued instructions
covering his intended operations. They contemplated that Sherman's
column, which was arriving by the north bank of the Tennessee, should
cross the river on a pontoon bridge just below the mouth of
Chickamauga Creek and carry the northern extremity of Missionary
Ridge as far as the railroad tunnel; that the Army of the Cumberland
--the centre--should co-operate with Sherman; and that Hooker with a
mixed command should continue to hold Lookout Valley and operate on
our extreme right as circumstances might warrant. Sherman crossed on
the 24th to perform his alloted part of the programme, but in the
meantime Grant becoming impressed with the idea that Bragg was
endeavoring to get away, ordered Thomas to make a strong
demonstration in his front, to determine the truth or falsity of the
information that had been received. This task fell to the Fourth
Corps, and at 12 o'clock on the 23d I was notified that Wood's
division would make a reconnoissance to an elevated point in its
front called Orchard Knob, and that I was to support it with my