d's army behind him?

A change of base to Savannah or Mobile had been contemplated as a
probable necessity of future operations in Georgia or in the Gulf
States, upon the capture of Atlanta; but that of course upon the
supposition that there would still be a formidable army of the
Confederacy in those States against which operations were to be
conducted. When that Confederate army, under Hood, marched toward
the west, with the evident intention to carry the war into Tennessee
and Kentucky, why a change of base by Sherman in the opposite
direction, to Savannah?

Sherman appears to have supposed at first that Hood would follow
him when he started on his march through Georgia, as Hood had
supposed that Sherman would follow him into Tennessee. Was there
any more reason for the one supposition than the other? Ought not
Sherman as well as Hood to have known his antagonist better than
such a supposition would imply? Was it not extremely unreasonable
to suppose that Hood, after he had marched hundreds of miles west
from Atlanta and reached the base of his projected operations in
Tennessee, would turn back and follow Sherman at such a distance
in his rear? It is perfectly evident that such a stern-chase by
Hood was contemplated only as a bare possibility, not by any means
as a probable result of Sherman's march. It could have had no
influence in forming Sherman's final determination to make that
march. In fact, the march does not appear to have been finally
decided on--certainly it was not commenced--until Hood had gone so
far in the opposite direction as to make his pursuit of Sherman
out of the question, and had fully disclosed his plan to invade
Tennessee. It was surely, therefore, an extraordinary spectacle
to see the main Union army marching where there was no considerable
hostile force to meet it, leaving a comparatively small detachment
to cope with the formidable enemy!

Of course Sherman could not fall back into Tennessee, and thus let
Hood put him on the defensive, even for a short time. He could
afford only to send back a detachment large enough to enable Thomas,
with the other forces he could assemble, to hold Nashville and
prevent Hood from crossing the Cumberland. This is virtually but
little more than what Sherman did in that regard.

THE MILITARY THEORY ON WHICH IT WAS BASED

There then remained to Sherman practically only one line of action
at all consistent wit