The 13th/16th Georgia Calvary Battalion is listed in some documentation as being the 1st Battalion Partisan Rangers. The original organization raised in various Georgia Counties was designated as the 16Th Battalion Georgia Cavalry.
The 16Th Battalion Georgia Cavalry was combined with other cavalry units in May 1864 and designated as the 13Th Battalion Georgia Cavalry. The combining of various cavalry units was necessary because of casualties and a high rate of desertions which caused an insufficient number of men to be available from the original 16Th Battalion to maintain the required number of companies required to form a battalion and also the lack of serviceable horses in sufficient numbers to mount all of the men in who were members of the original 16th Battalion which were transferred into the 13Th Battalion Georgia Cavalry. Some of the unmounted men likely were designated as infantry, but I have no documentation to prove that some members were assigned to infantry companies.
Most individuals who survived the war and who were members of the 13Th or 16Th Battalion have documents showing service in both battalions because new files were not established for the men when they became re-designated as members of the newly established 13Th Battalion. In fact, the men mostly we transferred to different companies when they were re-designated as the 13Th Battalion.
I believe that there was a 16Th Regiment of Cavalry in the Georgia State Guard Service(John Brown's Pets)prior to the 16Th Battalion being accepted into the Confederate regular service. I may be incorrect in this statement since I cannot lay my hands on the source from which the information concerning the 16th Regiment Georgia Cavalry was obtained.
My GG Grandfather's service record documents refer to his various activities as being in the 16th Battalion as well as the 13th Battalion.
Hope this post has not made your questions even more confusing.