Fffffft! Message for you, sir.

The key was: BALTIMORE. The red text is the cryptext.

Sep. 12th
THE ENEMY RAPIDLY CONCEN[T]RATING AT LOUIS[V]ILLE AND COVINGTON. THEY ARE CONFI[D]E[N]T OF SOON CRUSHING MY FORCE HERE IT IS IMPORTANT OUR COMMUNICATION WITH EACH OTHER S[H]OULD BE KEPT OPE[N] I SHALL PRES[E]NT A BOL[D] FRONT IN ORDER TO DECEIVE THE ENEMY AS LONG AS POSSIBLE AND WHEN COMPELLED I SHALL FALL BACK UPON YOU. MARSHALL IS STILL FAR BEHI[N]D. E.K.S. Sep 13 - A part of Genl Grant’s army is reported to have arrived at Louisville. Buell was expected to come on in advance of his army, and to arrive there yesterday. Several old batteries have arrived there within the past few days.
E.K.S.

General Edmund Kirby-Smith’s missive was probably sent to General Bragg who was headed towards Munfordville to join forces before marching to Louisville. The Union troops had set up a garrison at Munfordville and had repelled the initial Confederate attack. The siege lasted from the 14th until the 17th of September. Bragg’s troops arrived on the 15th and 16th and surrounded the garrison. On the 17th, they appeared and overwhelmed the Union.

Bastards.