This study concerns an analysis of the Confederate defense of Vicksburg with respect to one of the nine principles of war, the principle of the offensive. The problem in the study was to determine if Lieutenant General John C. Pemberton ever applied tho principle of the offensive during his defense of Vicksburg and to determine why he failed to gain any freedom of action during the Vicksburg Campaign. The important conclusions are: 1. Pemberton applied the principle prior to May 1, 1863. 2. He did not apply the principle during the final Union thrust for Vicksburg, mainly because of the lack of cavalry and of intelligence.