This Confederate order was written by Capt. William Henry Whitner who was appointed as the A. A. G. to Brig. Gen. Roger Atkinson Pryor on the Blackwater below Petersburg. Whitner began his Confederate service as a 2nd Lieutenant in Co. F, 1st Florida Infantry. He later suffered a gunshot wound to his little finger (resulting in its amputation) received during the Battle of the Wilderness on 6 May 1864. He finished the war in April 1865 serving as the A.A. G. Gen. B. R. Johnson’s Division, R. H. Anderson’s Corps.
Whitner wrote the order at the request and for the signature of his commander, Brig. Gen. Roger A. Pryor who filled a rank within the Confederate service far beyond his worth. The biographical sketch in Wikipedia is kinder than most in describing Pryor’s military performance:
“He entered the Confederate army as colonel of the 3rd Virginia Infantry Regiment. He was promoted to brigadier general on April 16, 1862. His brigade fought in the Peninsula Campaign and at Second Manassas, where it became detached in the swirling fighting and temporarily operated under Stonewall Jackson. Pryor’s command initially consisted of the 2nd Florida, 14th Alabama, 3rd Virginia, and 14th Louisiana. During the Seven Days Battles, the 1st (Coppens’) Louisiana Zouave Battalion was temporarily attached to it. Afterwards, the Louisianans departed and Pryor received two brand-new regiments; the 5th and 8th Florida Infantry. As a consequence, it became known as “The Florida Brigade.” At Antietam on September 17, 1862, he assumed command of Anderson’s Division in Longstreet’s Corps when Maj. Gen. Richard H. Anderson was wounded. Pryor proved inept as a division commander, and Union troops flanked his position, causing them to fall back in disorder. As a result, he did not gain a permanent higher field command from the Confederate president. Following his adequate performance at the Battle of Deserted House, later in 1863 Pryor resigned his commission and his brigade was broken up, its regiments being reassigned to other commands. In August of that year, he enlisted as a private and scout in the 3rd Virginia Cavalry Regiment under General Fitzhugh Lee. Pryor was captured on November 28, 1864, and confined in Fort Lafayette in New York as a suspected spy. After several months, he was released on parole by order of President Lincoln and returned to Virginia. CSA War Clerk and diarist, John B. Jones, mentioned Pryor in his April 9, 1865 entry from Richmond, VA, “Roger A. Pryor is said to have remained voluntarily in Petersburg, and announces his abandonment of the Confederate States cause.” [Wikipedia]

Transcription
Headquarters Forces on Black Water
December 21st 1862
General Order No. 13
The crime of desertion having become scandalously prevalent in this command, it is hereby ordered that any person of this command caught two miles from this camp without a proper pass and indicating a purpose to desert shall be shot at once without the formality of a trial. To this end, persons so caught will be immediately sent to these headquarters with the witnesses in the case.
By command of Brig. General Pryor
W. H. Witner, A. A. G.
