Burnside and the War Department both thought the 9th corps was intended
for such an expedition up to the last moment.

My general plan now was to concentrate all the force possible against
the Confederate armies in the field. There were but two such, as we
have seen, east of the Mississippi River and facing north. The Army of
Northern Virginia, General Robert E. Lee commanding, was on the south
bank of the Rapidan, confronting the Army of the Potomac; the second,
under General Joseph E. Johnston, was at Dalton, Georgia, opposed to
Sherman who was still at Chattanooga. Beside these main armies the
Confederates had to guard the Shenandoah Valley, a great storehouse to
feed their armies from, and their line of communications from Richmond
to Tennessee. Forrest, a brave and intrepid cavalry general, was in the
West with a large force; making a larger command necessary to hold what
we had gained in Middle and West Tennessee. We could not abandon any
territory north of the line held by the enemy because it would lay the
Northern States open to invasion. But as the Army of the Potomac was
the principal garrison for the protection of Washington even while it
was moving on Lee, so all the forces to the west, and the Army of the
James, guarded their special trusts when advancing from them as well as
when remaining at them. Better indeed, for they forced the enemy to
guard his own lines and resources at a greater distance from ours, and
with a greater force. Little expeditions could not so well be sent out
to destroy a bridge or tear up a few miles of railroad track, burn a
storehouse, or inflict other little annoyances. Accordingly I arranged
for a simultaneous movement all along the line. Sherman was to move
from Chattanooga, Johnston's army and Atlanta being his objective
points. (*23) Crook, commanding in West Virginia, was to move from the
mouth of the Gauley River with a cavalry force and some artillery, the
Virginia and Tennessee Railroad to be his objective. Either the enemy
would have to keep a large force to protect their communications, or see
them destroyed and a large amount of forage and provision, which they so
much needed, fall into our hands. Sigel was in command in the Valley of
Virginia. He was to advance up the valley, covering the North from an
invasion through that channel as well while advancing as by remaining
near Harper's Ferry. Every mile he advanced also gave us possession of
stores on whi