After Shiloh, why did Grant not move directly South to attack Vicksburg from the rear, rather than use the Mississippi?

Even today, going down US 45 to Tupelo, across the Natchez Trace to US 82, across to I-55, then down to Jackson and across I-20 to Vicksburg is a pain in the rear. Going across the geography of the time, without lines of supply, would have cost more casualties than did Shiloh.

Grant was an unimaginative pounder as a commanding general - you can't expect any great strategic insight or bold moves from such a general.If one believed in reincarnation,he came back as Bernard Montgomery.

He was caught with his trousers down at Shiloh and,but for the death of Johnston on the first day at Shiloh would have suffered a heavy - and career ending (given Lincoln's penchant for firing off losing generals 1861 through 1863) - defeat.

'reincarnated as Montgomery'....ROTFLMAO!...best non obscene description I ever heard of Montgomery

but back to your question. Engraved in every military schools is the adage 'Amateurs study tactics.Professionals study logistics".

All those great battles, from Persepolis to Inchon and Hue and whatever is happening tonight would never have happened if the soldiers hadn't been transported there, along with food, bullets, tents ,etc etc etc.....

As De Wit says, even today driving around there is a pain. In the 1860's moving tens of thousands of men and hundreds of tons of supplies was almost impossible by road,and barely possible by rail. But by steamer on the rivers, a piece of cake.