ved the first blow. Soon after, a
still more heavy attack was made on the Army of the Tennessee, our
extreme left, which resulted in one of the severest and most closely
contested battles of the war, and in which the knightly McPherson
was killed.

METHOD OF TRANSMITTING MESSAGES IN CIPHER

Under the system enforced by the War Department in 1864-5, the
commanders of troops in the field were compelled to communicate
with each other either in plain language which the enemy could read
if a despatch fell into his hands, or else in a cipher which neither
of the commanders nor any of their staff officers could decipher.
They were made absolutely dependent upon the cipher-operators of
the telegraph corps. Of course all this cipher correspondence
between commanding generals was promptly transmitted to the War
Department, so that the Secretary could know what was going on as
well as anybody. Whatever may have been the object of this, perhaps
not difficult to conjecture, its effect was to make rapid correspondence
in cipher impossible when rapidity was most important and secrecy
most necessary. In previous years I and one at least of my staff
officers were always familiar with the cipher code, so that we
could together, as a rule, quickly unravel a knotty telegram.
Indeed, I once had to decipher a despatch to which I had no key,
except I knew from internal evidence that it must be under the War
Department code, though written in a different key. It was a
despatch from Grant, who was then besieging Vicksburg. It had been
sent to Memphis by steamer, and thence by telegraph to St. Louis,
the place from which Grant's army drew its supplies. A cipher
despatch sent under the circumstances from Grant to me, who was
not at that time under his command, must necessarily be of great
importance. My staff officer at once informed me that it was in
some key different from that we had in use. So I took the thing
in hand myself, and went to work by the simplest possible process,
but one sure to lead to the correct result in time--that is, to
make all possible arrangements of the words until one was found
that would convey a rational meaning. Commencing about 3 P. M.,
I reached the desired result at three in the morning. Early that
day a steamer was on the way down the river with the supplies Grant
wanted. I never told the general how he came to get his supplies
so promptly, but I imagined I knew w