## The Exchange and What It Meant
The prisoner exchange that freed Walker on August 12, 1864 (or August 9, by some accounts) is a specific historical event that carries more significance than a routine administrative exchange might suggest.
Prisoner exchanges between the Union and Confederate armies were governed by the Dix-Hill Cartel of July 1862, which established a formal equivalence system under which prisoners were exchanged based on their rank. A general was worth 46 privates; a lieutenant colonel was worth 10 privates; and so on down the ranks. When the exchange system was working, it allowed armies to return prisoners without the sustained expense of maintaining large prisoner-of-war camps.
By 1864 the exchange system had largely broken down over the question of Black Union soldiers — the Confederacy refused to treat captured Black soldiers as prisoners of war eligible for exchange, treating them instead as escaped slaves or insurgents. General Grant suspended general exchanges partly for this reason: he concluded that resuming exchanges benefited the Confederacy more than the Union, since the Confederacy was more desperate for manpower than the Union was.
Against this background, Walker’s exchange was notable. She was exchanged for a Confederate surgeon from Tennessee, a one-for-one exchange of medical personnel. This individual exchange outside the suspended general system suggests that both sides had a specific interest in the particular transaction. The Union wanted Walker back; the Confederacy wanted the Confederate surgeon. The exchange was negotiated as an individual deal.
The fact that Walker was exchanged as an equivalent for a Confederate surgeon is itself a data point in the question of her military status. She was treated, for purposes of exchange, as military medical personnel — equivalent to a Confederate surgeon, subject to the exchange protocols that governed military prisoners. This is not, legally, the same as being a commissioned officer. But it is not treatment consistent with the view that she was simply a civilian who happened to be near the front lines when she was captured.