It is a bit confusing. I'll need a bit of time to study further, but at first perusal I think all of these cards refer to the same man. The differences might all be due to clerical error, or, in some cases, difficulty understanding the German accent. He is shown as being in Co D, 4th(2nd) Cavalry (not Calvary), but also some of the POW cards indicate Co B, 4th Cavalry, and even once in Co. E, 4th Infantry. The reference to enlistment in Jackson is clearly in error, and while some cards show enlistment in Senatobia and others Holly Springs or Salem, they all show the same date and same enrolling officer. Company clerks could be prone to error - some more than others. An original company clerk could be replaced with another who didn't have the institutional knowledge of his predecessor.