It was not accidental that in February 1861 Jefferson Davis, a prominent slaveholder from Mississippi, was inaugurated at Montgomery, Alabama, as the new president of the Confederate States of America. Both states had long been at the center of antebellum political power, wielding the stunning influence wrought by cotton and slavery. While South Carolina led the secessionist impulse, the emerging Confederate project would almost certainly have faltered without the crucial support of the Deep South. The Lower South states that seceded in the winter of 1860–1 commanded great political and sectional influence, shaping how and when the incipient slaveholding republic would be formed. But with the advent of war in April 1861, military thinkers considered Mississippi and Alabama the constituent states of the Deep South, judging other parts of the rebellious South in wholly different strategic terms. Mississippi and Alabama indeed played central roles in the formation of the world’s largest slaveholding republic; they would accordingly feel the hard hand of war in response to that decision. Although both states did not incur the same kind of invasions and wartime scarring endured by Virginia, Tennessee, and Georgia, the Deep South functioned as a testing ground for some of the Civil War’s most transformative events, rooted almost entirely in the tense nature of civilian–military relations.